Revert "Require a reason when marking a server bad (#654)"

This reverts commit 4dbef49ec9.

.circleci/config.yml

@@ -63,6 +63,9 @@ jobs:
       - run:
           name: "Lint"
           command: "cargo fmt --check"
+      - run:
+          name: "Clippy"
+          command: "cargo clippy --all --all-targets -- -Dwarnings"
       - run:
           name: "Tests"
           command: "cargo clean && cargo build && cargo test && bash .circleci/run_tests.sh && .circleci/generate_coverage.sh"

.circleci/run_tests.sh

@@ -108,8 +108,24 @@ cd ../..
 pip3 install -r tests/python/requirements.txt
 python3 tests/python/tests.py || exit 1
 
+
+#
+# Go tests
+# Starts its own pgcat server
+#
+pushd tests/go
+/usr/local/go/bin/go test || exit 1
+popd
+
 start_pgcat "info"
 
+#
+# Rust tests
+#
+cd tests/rust
+cargo run
+cd ../../
+
 # Admin tests
 export PGPASSWORD=admin_pass
 psql -U admin_user -e -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW STATS' > /dev/null

.github/workflows/publish-deb-package.yml

@@ -4,7 +4,7 @@ on:
   workflow_dispatch:
     inputs:
       packageVersion:
-        default: "1.1.2-dev"
+        default: "1.1.2-dev1"
 jobs:
   build:
     strategy:

.gitignore

@@ -10,3 +10,4 @@ lcov.info
 dev/.bash_history
 dev/cache
 !dev/cache/.keepme
+.venv

CONFIG.md

@@ -259,22 +259,6 @@ Password to be used for connecting to servers to obtain the hash used for md5 au
 specified in `auth_query_user`. The connection will be established using the database configured in the pool.
 This parameter is inherited by every pool and can be redefined in pool configuration.
 
-### prepared_statements
-```
-path: general.prepared_statements
-default: false
-```
-
-Whether to use prepared statements or not.
-
-### prepared_statements_cache_size
-```
-path: general.prepared_statements_cache_size
-default: 500
-```
-
-Size of the prepared statements cache.
-
 ### dns_cache_enabled
 ```
 path: general.dns_cache_enabled
@@ -324,6 +308,15 @@ If the client doesn't specify, PgCat routes traffic to this role by default.
 `replica` round-robin between replicas only without touching the primary,
 `primary` all queries go to the primary unless otherwise specified.
 
+### prepared_statements_cache_size
+```
+path: general.prepared_statements_cache_size
+default: 0
+```
+
+Size of the prepared statements cache. 0 means disabled.
+TODO: update documentation
+
 ### query_parser_enabled
 ```
 path: pools.<pool_name>.query_parser_enabled

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 Thank you for contributing! Just a few tips here:
 
-1. `cargo fmt` your code before opening up a PR
+1. `cargo fmt` and `cargo clippy` your code before opening up a PR
 2. Run the test suite (e.g. `pgbench`) to make sure everything still works. The tests are in `.circleci/run_tests.sh`.
 3. Performance is important, make sure there are no regressions in your branch vs. `main`.
 

Cargo.lock

@@ -17,6 +17,17 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
+[[package]]
+name = "ahash"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2c99f64d1e06488f620f932677e24bc6e2897582980441ae90a671415bd7ec2f"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+ "version_check",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "1.0.2"
@@ -26,6 +37,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "allocator-api2"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0942ffc6dcaadf03badf6e6a2d0228460359d5e34b57ccdc720b7382dfbd5ec5"
+
 [[package]]
 name = "android-tzdata"
 version = "0.1.1"
@@ -553,6 +570,10 @@ name = "hashbrown"
 version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2c6201b9ff9fd90a5a3bac2e56a830d0caa509576f0e503818ee82c181b3437a"
+dependencies = [
+ "ahash",
+ "allocator-api2",
+]
 
 [[package]]
 name = "heck"
@@ -821,6 +842,15 @@ version = "0.4.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b06a4cde4c0f271a446782e3eff8de789548ce57dbc8eca9292c27f4a42004b4"
 
+[[package]]
+name = "lru"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1efa59af2ddfad1854ae27d75009d538d0998b4b2fd47083e743ac1a10e46c60"
+dependencies = [
+ "hashbrown 0.14.0",
+]
+
 [[package]]
 name = "lru-cache"
 version = "0.1.2"
@@ -990,7 +1020,7 @@ checksum = "9b2a4787296e9989611394c33f193f676704af1686e70b8f8033ab5ba9a35a94"
 
 [[package]]
 name = "pgcat"
-version = "1.1.2-dev"
+version = "1.1.2-dev4"
 dependencies = [
  "arc-swap",
  "async-trait",
@@ -1008,6 +1038,7 @@ dependencies = [
  "itertools",
  "jemallocator",
  "log",
+ "lru",
  "md-5",
  "nix",
  "num_cpus",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pgcat"
-version = "1.1.2-dev"
+version = "1.1.2-dev4"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
@@ -48,6 +48,7 @@ itertools = "0.10"
 clap = { version = "4.3.1", features = ["derive", "env"] }
 tracing = "0.1.37"
 tracing-subscriber = { version = "0.3.17", features = ["json", "env-filter", "std"]}
+lru = "0.12.0"
 
 [target.'cfg(not(target_env = "msvc"))'.dependencies]
 jemallocator = "0.5.0"

Dockerfile

@@ -8,6 +8,12 @@ WORKDIR /app
 RUN cargo build --release
 
 FROM debian:bookworm-slim
+RUN apt-get update && apt-get install  -o Dpkg::Options::=--force-confdef -yq --no-install-recommends \
+    postgresql-client \
+    # Clean up layer
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
+    && truncate -s 0 /var/log/*log
 COPY --from=builder /app/target/release/pgcat /usr/bin/pgcat
 COPY --from=builder /app/pgcat.toml /etc/pgcat/pgcat.toml
 WORKDIR /etc/pgcat

Dockerfile.ci

@@ -9,6 +9,9 @@ RUN sudo apt-get update && \
 	sudo apt-get upgrade curl && \
 	cargo install cargo-binutils rustfilt && \
 	rustup component add llvm-tools-preview && \
- 	pip3 install psycopg2 && sudo gem install bundler && \
+	pip3 install psycopg2 && sudo gem install bundler && \
 	wget -O /tmp/toxiproxy-2.4.0.deb https://github.com/Shopify/toxiproxy/releases/download/v2.4.0/toxiproxy_2.4.0_linux_$(dpkg --print-architecture).deb && \
 	sudo dpkg -i /tmp/toxiproxy-2.4.0.deb
+RUN wget -O /tmp/go1.21.3.linux-$(dpkg --print-architecture).tar.gz https://go.dev/dl/go1.21.3.linux-$(dpkg --print-architecture).tar.gz && \
+    sudo tar -C /usr/local -xzf /tmp/go1.21.3.linux-$(dpkg --print-architecture).tar.gz && \
+    rm /tmp/go1.21.3.linux-$(dpkg --print-architecture).tar.gz

README.md

@@ -40,7 +40,7 @@ PgCat is stable and used in production to serve hundreds of thousands of queries
       </a>
     </td>
     <td>
-      <a href="https://postgresml.org/blog/scaling-postgresml-to-one-million-requests-per-second">
+      <a href="https://postgresml.org/blog/scaling-postgresml-to-1-million-requests-per-second">
         <img src="./images/postgresml.webp" height="70" width="auto">
       </a>
     </td>
@@ -57,7 +57,7 @@ PgCat is stable and used in production to serve hundreds of thousands of queries
       </a>
     </td>
     <td>
-      <a href="https://postgresml.org/blog/scaling-postgresml-to-one-million-requests-per-second">
+      <a href="https://postgresml.org/blog/scaling-postgresml-to-1-million-requests-per-second">
         PostgresML
       </a>
     </td>

dev/Dockerfile

@@ -1,6 +1,8 @@
 FROM rust:1.70-bullseye
 
 # Dependencies
+COPY --from=sclevine/yj /bin/yj /bin/yj
+RUN /bin/yj -h
 RUN apt-get update -y \
     && apt-get install -y \
     llvm-11 psmisc postgresql-contrib postgresql-client \

pgcat.toml

@@ -60,12 +60,6 @@ tcp_keepalives_count = 5
 # Number of seconds between keepalive packets.
 tcp_keepalives_interval = 5
 
-# Handle prepared statements.
-prepared_statements = true
-
-# Prepared statements server cache size.
-prepared_statements_cache_size = 500
-
 # Path to TLS Certificate file to use for TLS connections
 # tls_certificate = ".circleci/server.cert"
 # Path to TLS private key file to use for TLS connections
@@ -156,6 +150,10 @@ load_balancing_mode = "random"
 # `primary` all queries go to the primary unless otherwise specified.
 default_role = "any"
 
+# Prepared statements cache size.
+# TODO: update documentation
+prepared_statements_cache_size = 500
+
 # If Query Parser is enabled, we'll attempt to parse
 # every incoming query to determine if it's a read or a write.
 # If it's a read query, we'll direct it to a replica. Otherwise, if it's a write,
@@ -303,6 +301,8 @@ username = "other_user"
 password = "other_user"
 pool_size = 21
 statement_timeout = 15000
+connect_timeout = 1000
+idle_timeout = 1000
 
 # Shard configs are structured as pool.<pool_name>.shards.<shard_id>
 # Each shard config contains a list of servers that make up the shard

src/admin.rs

@@ -283,7 +283,7 @@ where
 {
     let mut res = BytesMut::new();
 
-    let detail_msg = vec![
+    let detail_msg = [
         "",
         "SHOW HELP|CONFIG|DATABASES|POOLS|CLIENTS|SERVERS|USERS|VERSION",
         // "SHOW PEERS|PEER_POOLS", // missing PEERS|PEER_POOLS
@@ -301,7 +301,6 @@ where
         // "KILL <db>",
         // "SUSPEND",
         "SHUTDOWN",
-        // "WAIT_CLOSE [<db>]", // missing
     ];
 
     res.put(notify("Console usage", detail_msg.join("\n\t")));
@@ -691,6 +690,8 @@ where
         ("query_count", DataType::Numeric),
         ("error_count", DataType::Numeric),
         ("age_seconds", DataType::Numeric),
+        ("maxwait", DataType::Numeric),
+        ("maxwait_us", DataType::Numeric),
     ];
 
     let new_map = get_client_stats();
@@ -698,6 +699,7 @@ where
     res.put(row_description(&columns));
 
     for (_, client) in new_map {
+        let max_wait = client.max_wait_time.load(Ordering::Relaxed);
         let row = vec![
             format!("{:#010X}", client.client_id()),
             client.pool_name(),
@@ -711,6 +713,8 @@ where
                 .duration_since(client.connect_time())
                 .as_secs()
                 .to_string(),
+            (max_wait / 1_000_000).to_string(),
+            (max_wait % 1_000_000).to_string(),
         ];
 
         res.put(data_row(&row));
@@ -745,6 +749,7 @@ where
         ("age_seconds", DataType::Numeric),
         ("prepare_cache_hit", DataType::Numeric),
         ("prepare_cache_miss", DataType::Numeric),
+        ("prepare_cache_eviction", DataType::Numeric),
         ("prepare_cache_size", DataType::Numeric),
     ];
 
@@ -777,6 +782,10 @@ where
                 .prepared_miss_count
                 .load(Ordering::Relaxed)
                 .to_string(),
+            server
+                .prepared_eviction_count
+                .load(Ordering::Relaxed)
+                .to_string(),
             server
                 .prepared_cache_size
                 .load(Ordering::Relaxed)
@@ -802,7 +811,7 @@ where
     T: tokio::io::AsyncWrite + std::marker::Unpin,
 {
     let parts: Vec<&str> = match tokens.len() == 2 {
-        true => tokens[1].split(",").map(|part| part.trim()).collect(),
+        true => tokens[1].split(',').map(|part| part.trim()).collect(),
         false => Vec::new(),
     };
 
@@ -865,7 +874,7 @@ where
     T: tokio::io::AsyncWrite + std::marker::Unpin,
 {
     let parts: Vec<&str> = match tokens.len() == 2 {
-        true => tokens[1].split(",").map(|part| part.trim()).collect(),
+        true => tokens[1].split(',').map(|part| part.trim()).collect(),
         false => Vec::new(),
     };
 

src/auth_passthrough.rs

@@ -79,6 +79,8 @@ impl AuthPassthrough {
             pool_mode: None,
             server_lifetime: None,
             min_pool_size: None,
+            connect_timeout: None,
+            idle_timeout: None,
         };
 
         let user = &address.username;

src/cmd_args.rs

@@ -25,7 +25,7 @@ pub struct Args {
 }
 
 pub fn parse() -> Args {
-    return Args::parse();
+    Args::parse()
 }
 
 #[derive(ValueEnum, Clone, Debug)]

src/config.rs

@@ -1,6 +1,6 @@
 /// Parse the configuration file.
 use arc_swap::ArcSwap;
-use log::{error, info, warn};
+use log::{error, info};
 use once_cell::sync::Lazy;
 use regex::Regex;
 use serde::{Deserializer, Serializer};
@@ -116,10 +116,10 @@ impl Default for Address {
             host: String::from("127.0.0.1"),
             port: 5432,
             shard: 0,
-            address_index: 0,
-            replica_number: 0,
             database: String::from("database"),
             role: Role::Replica,
+            replica_number: 0,
+            address_index: 0,
             username: String::from("username"),
             pool_name: String::from("pool_name"),
             mirrors: Vec::new(),
@@ -216,6 +216,8 @@ pub struct User {
     pub server_lifetime: Option<u64>,
     #[serde(default)] // 0
     pub statement_timeout: u64,
+    pub connect_timeout: Option<u64>,
+    pub idle_timeout: Option<u64>,
 }
 
 impl Default for User {
@@ -230,24 +232,22 @@ impl Default for User {
             statement_timeout: 0,
             pool_mode: None,
             server_lifetime: None,
+            connect_timeout: None,
+            idle_timeout: None,
         }
     }
 }
 
 impl User {
     fn validate(&self) -> Result<(), Error> {
-        match self.min_pool_size {
-            Some(min_pool_size) => {
-                if min_pool_size > self.pool_size {
-                    error!(
-                        "min_pool_size of {} cannot be larger than pool_size of {}",
-                        min_pool_size, self.pool_size
-                    );
-                    return Err(Error::BadConfig);
-                }
+        if let Some(min_pool_size) = self.min_pool_size {
+            if min_pool_size > self.pool_size {
+                error!(
+                    "min_pool_size of {} cannot be larger than pool_size of {}",
+                    min_pool_size, self.pool_size
+                );
+                return Err(Error::BadConfig);
             }
-
-            None => (),
         };
 
         Ok(())
@@ -341,12 +341,6 @@ pub struct General {
     pub auth_query: Option<String>,
     pub auth_query_user: Option<String>,
     pub auth_query_password: Option<String>,
-
-    #[serde(default)]
-    pub prepared_statements: bool,
-
-    #[serde(default = "General::default_prepared_statements_cache_size")]
-    pub prepared_statements_cache_size: usize,
 }
 
 impl General {
@@ -428,10 +422,6 @@ impl General {
     pub fn default_server_round_robin() -> bool {
         true
     }
-
-    pub fn default_prepared_statements_cache_size() -> usize {
-        500
-    }
 }
 
 impl Default for General {
@@ -443,35 +433,33 @@ impl Default for General {
             prometheus_exporter_port: 9930,
             connect_timeout: General::default_connect_timeout(),
             idle_timeout: General::default_idle_timeout(),
-            shutdown_timeout: Self::default_shutdown_timeout(),
-            healthcheck_timeout: Self::default_healthcheck_timeout(),
-            healthcheck_delay: Self::default_healthcheck_delay(),
-            ban_time: Self::default_ban_time(),
-            worker_threads: Self::default_worker_threads(),
-            idle_client_in_transaction_timeout: Self::default_idle_client_in_transaction_timeout(),
             tcp_keepalives_idle: Self::default_tcp_keepalives_idle(),
             tcp_keepalives_count: Self::default_tcp_keepalives_count(),
             tcp_keepalives_interval: Self::default_tcp_keepalives_interval(),
             tcp_user_timeout: Self::default_tcp_user_timeout(),
             log_client_connections: false,
             log_client_disconnections: false,
-            autoreload: None,
             dns_cache_enabled: false,
             dns_max_ttl: Self::default_dns_max_ttl(),
+            shutdown_timeout: Self::default_shutdown_timeout(),
+            healthcheck_timeout: Self::default_healthcheck_timeout(),
+            healthcheck_delay: Self::default_healthcheck_delay(),
+            ban_time: Self::default_ban_time(),
+            idle_client_in_transaction_timeout: Self::default_idle_client_in_transaction_timeout(),
+            server_lifetime: Self::default_server_lifetime(),
+            server_round_robin: Self::default_server_round_robin(),
+            worker_threads: Self::default_worker_threads(),
+            autoreload: None,
             tls_certificate: None,
             tls_private_key: None,
             server_tls: false,
             verify_server_certificate: false,
             admin_username: String::from("admin"),
             admin_password: String::from("admin"),
+            validate_config: true,
             auth_query: None,
             auth_query_user: None,
             auth_query_password: None,
-            server_lifetime: Self::default_server_lifetime(),
-            server_round_robin: Self::default_server_round_robin(),
-            validate_config: true,
-            prepared_statements: false,
-            prepared_statements_cache_size: 500,
         }
     }
 }
@@ -572,6 +560,9 @@ pub struct Pool {
     #[serde(default)] // False
     pub log_client_parameter_status_changes: bool,
 
+    #[serde(default = "Pool::default_prepared_statements_cache_size")]
+    pub prepared_statements_cache_size: usize,
+
     pub plugins: Option<Plugins>,
     pub shards: BTreeMap<String, Shard>,
     pub users: BTreeMap<String, User>,
@@ -621,6 +612,10 @@ impl Pool {
         true
     }
 
+    pub fn default_prepared_statements_cache_size() -> usize {
+        0
+    }
+
     pub fn validate(&mut self) -> Result<(), Error> {
         match self.default_role.as_ref() {
             "any" => (),
@@ -677,9 +672,9 @@ impl Pool {
             Some(key) => {
                 // No quotes in the key so we don't have to compare quoted
                 // to unquoted idents.
-                let key = key.replace("\"", "");
+                let key = key.replace('\"', "");
 
-                if key.split(".").count() != 2 {
+                if key.split('.').count() != 2 {
                     error!(
                         "automatic_sharding_key '{}' must be fully qualified, e.g. t.{}`",
                         key, key
@@ -692,17 +687,14 @@ impl Pool {
             None => None,
         };
 
-        match self.default_shard {
-            DefaultShard::Shard(shard_number) => {
-                if shard_number >= self.shards.len() {
-                    error!("Invalid shard {:?}", shard_number);
-                    return Err(Error::BadConfig);
-                }
+        if let DefaultShard::Shard(shard_number) = self.default_shard {
+            if shard_number >= self.shards.len() {
+                error!("Invalid shard {:?}", shard_number);
+                return Err(Error::BadConfig);
             }
-            _ => (),
         }
 
-        for (_, user) in &self.users {
+        for user in self.users.values() {
             user.validate()?;
         }
 
@@ -715,17 +707,16 @@ impl Default for Pool {
         Pool {
             pool_mode: Self::default_pool_mode(),
             load_balancing_mode: Self::default_load_balancing_mode(),
-            shards: BTreeMap::from([(String::from("1"), Shard::default())]),
-            users: BTreeMap::default(),
             default_role: String::from("any"),
             query_parser_enabled: false,
             query_parser_max_length: None,
             query_parser_read_write_splitting: false,
             primary_reads_enabled: false,
-            sharding_function: ShardingFunction::PgBigintHash,
-            automatic_sharding_key: None,
             connect_timeout: None,
             idle_timeout: None,
+            server_lifetime: None,
+            sharding_function: ShardingFunction::PgBigintHash,
+            automatic_sharding_key: None,
             sharding_key_regex: None,
             shard_id_regex: None,
             regex_search_limit: Some(1000),
@@ -733,10 +724,12 @@ impl Default for Pool {
             auth_query: None,
             auth_query_user: None,
             auth_query_password: None,
-            server_lifetime: None,
-            plugins: None,
             cleanup_server_connections: true,
             log_client_parameter_status_changes: false,
+            prepared_statements_cache_size: Self::default_prepared_statements_cache_size(),
+            plugins: None,
+            shards: BTreeMap::from([(String::from("1"), Shard::default())]),
+            users: BTreeMap::default(),
         }
     }
 }
@@ -777,8 +770,8 @@ impl<'de> serde::Deserialize<'de> for DefaultShard {
         D: Deserializer<'de>,
     {
         let s = String::deserialize(deserializer)?;
-        if s.starts_with("shard_") {
-            let shard = s[6..].parse::<usize>().map_err(serde::de::Error::custom)?;
+        if let Some(s) = s.strip_prefix("shard_") {
+            let shard = s.parse::<usize>().map_err(serde::de::Error::custom)?;
             return Ok(DefaultShard::Shard(shard));
         }
 
@@ -848,13 +841,13 @@ impl Shard {
 impl Default for Shard {
     fn default() -> Shard {
         Shard {
+            database: String::from("postgres"),
+            mirrors: None,
             servers: vec![ServerConfig {
                 host: String::from("localhost"),
                 port: 5432,
                 role: Role::Primary,
             }],
-            mirrors: None,
-            database: String::from("postgres"),
         }
     }
 }
@@ -867,15 +860,26 @@ pub struct Plugins {
     pub prewarmer: Option<Prewarmer>,
 }
 
+pub trait Plugin {
+    fn is_enabled(&self) -> bool;
+}
+
 impl std::fmt::Display for Plugins {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        fn is_enabled<T: Plugin>(arg: Option<&T>) -> bool {
+            if let Some(arg) = arg {
+                arg.is_enabled()
+            } else {
+                false
+            }
+        }
         write!(
             f,
             "interceptor: {}, table_access: {}, query_logger: {}, prewarmer: {}",
-            self.intercept.is_some(),
-            self.table_access.is_some(),
-            self.query_logger.is_some(),
-            self.prewarmer.is_some(),
+            is_enabled(self.intercept.as_ref()),
+            is_enabled(self.table_access.as_ref()),
+            is_enabled(self.query_logger.as_ref()),
+            is_enabled(self.prewarmer.as_ref()),
         )
     }
 }
@@ -886,23 +890,47 @@ pub struct Intercept {
     pub queries: BTreeMap<String, Query>,
 }
 
+impl Plugin for Intercept {
+    fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, Hash, Eq)]
 pub struct TableAccess {
     pub enabled: bool,
     pub tables: Vec<String>,
 }
 
+impl Plugin for TableAccess {
+    fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, Hash, Eq)]
 pub struct QueryLogger {
     pub enabled: bool,
 }
 
+impl Plugin for QueryLogger {
+    fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, Hash, Eq)]
 pub struct Prewarmer {
     pub enabled: bool,
     pub queries: Vec<String>,
 }
 
+impl Plugin for Prewarmer {
+    fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+}
+
 impl Intercept {
     pub fn substitute(&mut self, db: &str, user: &str) {
         for (_, query) in self.queries.iter_mut() {
@@ -920,6 +948,7 @@ pub struct Query {
 }
 
 impl Query {
+    #[allow(clippy::needless_range_loop)]
     pub fn substitute(&mut self, db: &str, user: &str) {
         for col in self.result.iter_mut() {
             for i in 0..col.len() {
@@ -989,8 +1018,8 @@ impl Default for Config {
         Config {
             path: Self::default_path(),
             general: General::default(),
-            pools: HashMap::default(),
             plugins: None,
+            pools: HashMap::default(),
         }
     }
 }
@@ -1044,8 +1073,8 @@ impl From<&Config> for std::collections::HashMap<String, String> {
                     (
                         format!("pools.{:?}.users", pool_name),
                         pool.users
-                            .iter()
-                            .map(|(_username, user)| &user.username)
+                            .values()
+                            .map(|user| &user.username)
                             .cloned()
                             .collect::<Vec<String>>()
                             .join(", "),
@@ -1099,6 +1128,7 @@ impl From<&Config> for std::collections::HashMap<String, String> {
 impl Config {
     /// Print current configuration.
     pub fn show(&self) {
+        info!("Config path: {}", self.path);
         info!("Ban time: {}s", self.general.ban_time);
         info!(
             "Idle client in transaction timeout: {}ms",
@@ -1130,13 +1160,9 @@ impl Config {
             Some(tls_certificate) => {
                 info!("TLS certificate: {}", tls_certificate);
 
-                match self.general.tls_private_key.clone() {
-                    Some(tls_private_key) => {
-                        info!("TLS private key: {}", tls_private_key);
-                        info!("TLS support is enabled");
-                    }
-
-                    None => (),
+                if let Some(tls_private_key) = self.general.tls_private_key.clone() {
+                    info!("TLS private key: {}", tls_private_key);
+                    info!("TLS support is enabled");
                 }
             }
 
@@ -1149,13 +1175,6 @@ impl Config {
             "Server TLS certificate verification: {}",
             self.general.verify_server_certificate
         );
-        info!("Prepared statements: {}", self.general.prepared_statements);
-        if self.general.prepared_statements {
-            info!(
-                "Prepared statements server cache size: {}",
-                self.general.prepared_statements_cache_size
-            );
-        }
         info!(
             "Plugins: {}",
             match self.plugins {
@@ -1171,8 +1190,8 @@ impl Config {
                 pool_name,
                 pool_config
                     .users
-                    .iter()
-                    .map(|(_, user_cfg)| user_cfg.pool_size)
+                    .values()
+                    .map(|user_cfg| user_cfg.pool_size)
                     .sum::<u32>()
                     .to_string()
             );
@@ -1246,6 +1265,10 @@ impl Config {
                 "[pool: {}] Log client parameter status changes: {}",
                 pool_name, pool_config.log_client_parameter_status_changes
             );
+            info!(
+                "[pool: {}] Prepared statements server cache size: {}",
+                pool_name, pool_config.prepared_statements_cache_size
+            );
             info!(
                 "[pool: {}] Plugins: {}",
                 pool_name,
@@ -1288,6 +1311,24 @@ impl Config {
                         None => "default".to_string(),
                     }
                 );
+                info!(
+                    "[pool: {}][user: {}] Connection timeout: {}",
+                    pool_name,
+                    user.1.username,
+                    match user.1.connect_timeout {
+                        Some(connect_timeout) => format!("{}ms", connect_timeout),
+                        None => "not set".to_string(),
+                    }
+                );
+                info!(
+                    "[pool: {}][user: {}] Idle timeout: {}",
+                    pool_name,
+                    user.1.username,
+                    match user.1.idle_timeout {
+                        Some(idle_timeout) => format!("{}ms", idle_timeout),
+                        None => "not set".to_string(),
+                    }
+                );
             }
         }
     }
@@ -1342,42 +1383,31 @@ impl Config {
         }
 
         // Validate TLS!
-        match self.general.tls_certificate {
-            Some(ref mut tls_certificate) => {
-                match load_certs(Path::new(&tls_certificate)) {
-                    Ok(_) => {
-                        // Cert is okay, but what about the private key?
-                        match self.general.tls_private_key {
-                            Some(ref tls_private_key) => {
-                                match load_keys(Path::new(&tls_private_key)) {
-                                    Ok(_) => (),
-                                    Err(err) => {
-                                        warn!(
-                                            "tls_private_key is incorrectly configured: {:?}",
-                                            err
-                                        );
-                                        self.general.tls_private_key = None;
-                                        self.general.tls_certificate = None;
-                                    }
-                                }
+        if let Some(tls_certificate) = self.general.tls_certificate.clone() {
+            match load_certs(Path::new(&tls_certificate)) {
+                Ok(_) => {
+                    // Cert is okay, but what about the private key?
+                    match self.general.tls_private_key.clone() {
+                        Some(tls_private_key) => match load_keys(Path::new(&tls_private_key)) {
+                            Ok(_) => (),
+                            Err(err) => {
+                                error!("tls_private_key is incorrectly configured: {:?}", err);
+                                return Err(Error::BadConfig);
                             }
+                        },
 
-                            None => {
-                                warn!("tls_certificate is set, but the tls_private_key is not");
-                                self.general.tls_private_key = None;
-                                self.general.tls_certificate = None;
-                            }
-                        };
-                    }
+                        None => {
+                            error!("tls_certificate is set, but the tls_private_key is not");
+                            return Err(Error::BadConfig);
+                        }
+                    };
+                }
 
-                    Err(err) => {
-                        warn!("tls_certificate is incorrectly configured: {:?}", err);
-                        self.general.tls_private_key = None;
-                        self.general.tls_certificate = None;
-                    }
+                Err(err) => {
+                    error!("tls_certificate is incorrectly configured: {:?}", err);
+                    return Err(Error::BadConfig);
                 }
             }
-            None => (),
         };
 
         for pool in self.pools.values_mut() {
@@ -1399,14 +1429,6 @@ pub fn get_idle_client_in_transaction_timeout() -> u64 {
     CONFIG.load().general.idle_client_in_transaction_timeout
 }
 
-pub fn get_prepared_statements() -> bool {
-    CONFIG.load().general.prepared_statements
-}
-
-pub fn get_prepared_statements_cache_size() -> usize {
-    CONFIG.load().general.prepared_statements_cache_size
-}
-
 /// Parse the configuration file located at the path.
 pub async fn parse(path: &str) -> Result<(), Error> {
     let mut contents = String::new();

src/errors.rs

@@ -29,6 +29,7 @@ pub enum Error {
     QueryRouterParserError(String),
     QueryRouterError(String),
     InvalidShardId(usize),
+    PreparedStatementError,
 }
 
 #[derive(Clone, PartialEq, Debug)]

src/messages.rs

@@ -12,13 +12,16 @@ use crate::config::get_config;
 use crate::errors::Error;
 
 use crate::constants::MESSAGE_TERMINATOR;
+use std::collections::hash_map::DefaultHasher;
 use std::collections::HashMap;
 use std::ffi::CString;
 use std::fmt::{Display, Formatter};
+use std::hash::{Hash, Hasher};
 use std::io::{BufRead, Cursor};
 use std::mem;
 use std::str::FromStr;
 use std::sync::atomic::Ordering;
+use std::sync::Arc;
 use std::time::Duration;
 
 /// Postgres data type mappings
@@ -114,19 +117,11 @@ pub fn simple_query(query: &str) -> BytesMut {
 }
 
 /// Tell the client we're ready for another query.
-pub async fn ready_for_query<S>(stream: &mut S) -> Result<(), Error>
+pub async fn send_ready_for_query<S>(stream: &mut S) -> Result<(), Error>
 where
     S: tokio::io::AsyncWrite + std::marker::Unpin,
 {
-    let mut bytes = BytesMut::with_capacity(
-        mem::size_of::<u8>() + mem::size_of::<i32>() + mem::size_of::<u8>(),
-    );
-
-    bytes.put_u8(b'Z');
-    bytes.put_i32(5);
-    bytes.put_u8(b'I'); // Idle
-
-    write_all(stream, bytes).await
+    write_all(stream, ready_for_query(false)).await
 }
 
 /// Send the startup packet the server. We're pretending we're a Pg client.
@@ -163,12 +158,10 @@ where
 
     match stream.write_all(&startup).await {
         Ok(_) => Ok(()),
-        Err(err) => {
-            return Err(Error::SocketError(format!(
-                "Error writing startup to server socket - Error: {:?}",
-                err
-            )))
-        }
+        Err(err) => Err(Error::SocketError(format!(
+            "Error writing startup to server socket - Error: {:?}",
+            err
+        ))),
     }
 }
 
@@ -244,8 +237,8 @@ pub fn md5_hash_password(user: &str, password: &str, salt: &[u8]) -> Vec<u8> {
     let mut md5 = Md5::new();
 
     // First pass
-    md5.update(&password.as_bytes());
-    md5.update(&user.as_bytes());
+    md5.update(password.as_bytes());
+    md5.update(user.as_bytes());
 
     let output = md5.finalize_reset();
 
@@ -281,7 +274,7 @@ where
 {
     let password = md5_hash_password(user, password, salt);
 
-    let mut message = BytesMut::with_capacity(password.len() as usize + 5);
+    let mut message = BytesMut::with_capacity(password.len() + 5);
 
     message.put_u8(b'p');
     message.put_i32(password.len() as i32 + 4);
@@ -295,7 +288,7 @@ where
     S: tokio::io::AsyncWrite + std::marker::Unpin,
 {
     let password = md5_hash_second_pass(hash, salt);
-    let mut message = BytesMut::with_capacity(password.len() as usize + 5);
+    let mut message = BytesMut::with_capacity(password.len() + 5);
 
     message.put_u8(b'p');
     message.put_i32(password.len() as i32 + 4);
@@ -322,7 +315,7 @@ where
     res.put_slice(&set_complete[..]);
 
     write_all_half(stream, &res).await?;
-    ready_for_query(stream).await
+    send_ready_for_query(stream).await
 }
 
 /// Send a custom error message to the client.
@@ -333,7 +326,7 @@ where
     S: tokio::io::AsyncWrite + std::marker::Unpin,
 {
     error_response_terminal(stream, message).await?;
-    ready_for_query(stream).await
+    send_ready_for_query(stream).await
 }
 
 /// Send a custom error message to the client.
@@ -434,7 +427,7 @@ where
     res.put(command_complete("SELECT 1"));
 
     write_all_half(stream, &res).await?;
-    ready_for_query(stream).await
+    send_ready_for_query(stream).await
 }
 
 pub fn row_description(columns: &Vec<(&str, DataType)>) -> BytesMut {
@@ -516,7 +509,7 @@ pub fn data_row_nullable(row: &Vec<Option<String>>) -> BytesMut {
             data_row.put_i32(column.len() as i32);
             data_row.put_slice(column);
         } else {
-            data_row.put_i32(-1 as i32);
+            data_row.put_i32(-1_i32);
         }
     }
 
@@ -564,6 +557,37 @@ pub fn flush() -> BytesMut {
     bytes
 }
 
+pub fn sync() -> BytesMut {
+    let mut bytes = BytesMut::with_capacity(mem::size_of::<u8>() + mem::size_of::<i32>());
+    bytes.put_u8(b'S');
+    bytes.put_i32(4);
+    bytes
+}
+
+pub fn parse_complete() -> BytesMut {
+    let mut bytes = BytesMut::with_capacity(mem::size_of::<u8>() + mem::size_of::<i32>());
+
+    bytes.put_u8(b'1');
+    bytes.put_i32(4);
+    bytes
+}
+
+pub fn ready_for_query(in_transaction: bool) -> BytesMut {
+    let mut bytes = BytesMut::with_capacity(
+        mem::size_of::<u8>() + mem::size_of::<i32>() + mem::size_of::<u8>(),
+    );
+
+    bytes.put_u8(b'Z');
+    bytes.put_i32(5);
+    if in_transaction {
+        bytes.put_u8(b'T');
+    } else {
+        bytes.put_u8(b'I');
+    }
+
+    bytes
+}
+
 /// Write all data in the buffer to the TcpStream.
 pub async fn write_all<S>(stream: &mut S, buf: BytesMut) -> Result<(), Error>
 where
@@ -571,12 +595,10 @@ where
 {
     match stream.write_all(&buf).await {
         Ok(_) => Ok(()),
-        Err(err) => {
-            return Err(Error::SocketError(format!(
-                "Error writing to socket - Error: {:?}",
-                err
-            )))
-        }
+        Err(err) => Err(Error::SocketError(format!(
+            "Error writing to socket - Error: {:?}",
+            err
+        ))),
     }
 }
 
@@ -587,12 +609,10 @@ where
 {
     match stream.write_all(buf).await {
         Ok(_) => Ok(()),
-        Err(err) => {
-            return Err(Error::SocketError(format!(
-                "Error writing to socket - Error: {:?}",
-                err
-            )))
-        }
+        Err(err) => Err(Error::SocketError(format!(
+            "Error writing to socket - Error: {:?}",
+            err
+        ))),
     }
 }
 
@@ -603,19 +623,15 @@ where
     match stream.write_all(buf).await {
         Ok(_) => match stream.flush().await {
             Ok(_) => Ok(()),
-            Err(err) => {
-                return Err(Error::SocketError(format!(
-                    "Error flushing socket - Error: {:?}",
-                    err
-                )))
-            }
-        },
-        Err(err) => {
-            return Err(Error::SocketError(format!(
-                "Error writing to socket - Error: {:?}",
+            Err(err) => Err(Error::SocketError(format!(
+                "Error flushing socket - Error: {:?}",
                 err
-            )))
-        }
+            ))),
+        },
+        Err(err) => Err(Error::SocketError(format!(
+            "Error writing to socket - Error: {:?}",
+            err
+        ))),
     }
 }
 
@@ -730,7 +746,7 @@ impl BytesMutReader for Cursor<&BytesMut> {
         let mut buf = vec![];
         match self.read_until(b'\0', &mut buf) {
             Ok(_) => Ok(String::from_utf8_lossy(&buf[..buf.len() - 1]).to_string()),
-            Err(err) => return Err(Error::ParseBytesError(err.to_string())),
+            Err(err) => Err(Error::ParseBytesError(err.to_string())),
         }
     }
 }
@@ -746,10 +762,55 @@ impl BytesMutReader for BytesMut {
                 let string_bytes = self.split_to(index + 1);
                 Ok(String::from_utf8_lossy(&string_bytes[..string_bytes.len() - 1]).to_string())
             }
-            None => return Err(Error::ParseBytesError("Could not read string".to_string())),
+            None => Err(Error::ParseBytesError("Could not read string".to_string())),
         }
     }
 }
+
+pub enum ExtendedProtocolData {
+    Parse {
+        data: BytesMut,
+        metadata: Option<(Arc<Parse>, u64)>,
+    },
+    Bind {
+        data: BytesMut,
+        metadata: Option<String>,
+    },
+    Describe {
+        data: BytesMut,
+        metadata: Option<String>,
+    },
+    Execute {
+        data: BytesMut,
+    },
+    Close {
+        data: BytesMut,
+        close: Close,
+    },
+}
+
+impl ExtendedProtocolData {
+    pub fn create_new_parse(data: BytesMut, metadata: Option<(Arc<Parse>, u64)>) -> Self {
+        Self::Parse { data, metadata }
+    }
+
+    pub fn create_new_bind(data: BytesMut, metadata: Option<String>) -> Self {
+        Self::Bind { data, metadata }
+    }
+
+    pub fn create_new_describe(data: BytesMut, metadata: Option<String>) -> Self {
+        Self::Describe { data, metadata }
+    }
+
+    pub fn create_new_execute(data: BytesMut) -> Self {
+        Self::Execute { data }
+    }
+
+    pub fn create_new_close(data: BytesMut, close: Close) -> Self {
+        Self::Close { data, close }
+    }
+}
+
 /// Parse (F) message.
 /// See: <https://www.postgresql.org/docs/current/protocol-message-formats.html>
 #[derive(Clone, Debug)]
@@ -758,7 +819,6 @@ pub struct Parse {
     #[allow(dead_code)]
     len: i32,
     pub name: String,
-    pub generated_name: String,
     query: String,
     num_params: i16,
     param_types: Vec<i32>,
@@ -784,7 +844,6 @@ impl TryFrom<&BytesMut> for Parse {
             code,
             len,
             name,
-            generated_name: prepared_statement_name(),
             query,
             num_params,
             param_types,
@@ -833,11 +892,44 @@ impl TryFrom<&Parse> for BytesMut {
 }
 
 impl Parse {
-    pub fn rename(mut self) -> Self {
-        self.name = self.generated_name.to_string();
+    /// Renames the prepared statement to a new name based on the global counter
+    pub fn rewrite(mut self) -> Self {
+        self.name = format!(
+            "PGCAT_{}",
+            PREPARED_STATEMENT_COUNTER.fetch_add(1, Ordering::SeqCst)
+        );
         self
     }
 
+    /// Gets the name of the prepared statement from the buffer
+    pub fn get_name(buf: &BytesMut) -> Result<String, Error> {
+        let mut cursor = Cursor::new(buf);
+        // Skip the code and length
+        cursor.advance(mem::size_of::<u8>() + mem::size_of::<i32>());
+        cursor.read_string()
+    }
+
+    /// Hashes the parse statement to be used as a key in the global cache
+    pub fn get_hash(&self) -> u64 {
+        // TODO_ZAIN: Take a look at which hashing function is being used
+        let mut hasher = DefaultHasher::new();
+
+        let concatenated = format!(
+            "{}{}{}",
+            self.query,
+            self.num_params,
+            self.param_types
+                .iter()
+                .map(ToString::to_string)
+                .collect::<Vec<_>>()
+                .join(",")
+        );
+
+        concatenated.hash(&mut hasher);
+
+        hasher.finish()
+    }
+
     pub fn anonymous(&self) -> bool {
         self.name.is_empty()
     }
@@ -968,9 +1060,42 @@ impl TryFrom<Bind> for BytesMut {
 }
 
 impl Bind {
-    pub fn reassign(mut self, parse: &Parse) -> Self {
-        self.prepared_statement = parse.name.clone();
-        self
+    /// Gets the name of the prepared statement from the buffer
+    pub fn get_name(buf: &BytesMut) -> Result<String, Error> {
+        let mut cursor = Cursor::new(buf);
+        // Skip the code and length
+        cursor.advance(mem::size_of::<u8>() + mem::size_of::<i32>());
+        cursor.read_string()?;
+        cursor.read_string()
+    }
+
+    /// Renames the prepared statement to a new name
+    pub fn rename(buf: BytesMut, new_name: &str) -> Result<BytesMut, Error> {
+        let mut cursor = Cursor::new(&buf);
+        // Read basic data from the cursor
+        let code = cursor.get_u8();
+        let current_len = cursor.get_i32();
+        let portal = cursor.read_string()?;
+        let prepared_statement = cursor.read_string()?;
+
+        // Calculate new length
+        let new_len = current_len + new_name.len() as i32 - prepared_statement.len() as i32;
+
+        // Begin building the response buffer
+        let mut response_buf = BytesMut::with_capacity(new_len as usize + 1);
+        response_buf.put_u8(code);
+        response_buf.put_i32(new_len);
+
+        // Put the portal and new name into the buffer
+        // Note: panic if the provided string contains null byte
+        response_buf.put_slice(CString::new(portal)?.as_bytes_with_nul());
+        response_buf.put_slice(CString::new(new_name)?.as_bytes_with_nul());
+
+        // Add the remainder of the original buffer into the response
+        response_buf.put_slice(&buf[cursor.position() as usize..]);
+
+        // Return the buffer
+        Ok(response_buf)
     }
 
     pub fn anonymous(&self) -> bool {
@@ -984,7 +1109,7 @@ pub struct Describe {
 
     #[allow(dead_code)]
     len: i32,
-    target: char,
+    pub target: char,
     pub statement_name: String,
 }
 
@@ -1026,6 +1151,15 @@ impl TryFrom<Describe> for BytesMut {
 }
 
 impl Describe {
+    pub fn empty_new() -> Describe {
+        Describe {
+            code: 'D',
+            len: 4 + 1 + 1,
+            target: 'S',
+            statement_name: "".to_string(),
+        }
+    }
+
     pub fn rename(mut self, name: &str) -> Self {
         self.statement_name = name.to_string();
         self
@@ -1114,13 +1248,6 @@ pub fn close_complete() -> BytesMut {
     bytes
 }
 
-pub fn prepared_statement_name() -> String {
-    format!(
-        "P_{}",
-        PREPARED_STATEMENT_COUNTER.fetch_add(1, Ordering::SeqCst)
-    )
-}
-
 // from https://www.postgresql.org/docs/12/protocol-error-fields.html
 #[derive(Debug, Default, PartialEq)]
 pub struct PgErrorMsg {
@@ -1203,7 +1330,7 @@ impl Display for PgErrorMsg {
 }
 
 impl PgErrorMsg {
-    pub fn parse(error_msg: Vec<u8>) -> Result<PgErrorMsg, Error> {
+    pub fn parse(error_msg: &[u8]) -> Result<PgErrorMsg, Error> {
         let mut out = PgErrorMsg {
             severity_localized: "".to_string(),
             severity: "".to_string(),
@@ -1311,38 +1438,38 @@ mod tests {
     fn parse_fields() {
         let mut complete_msg = vec![];
         let severity = "FATAL";
-        complete_msg.extend(field('S', &severity));
-        complete_msg.extend(field('V', &severity));
+        complete_msg.extend(field('S', severity));
+        complete_msg.extend(field('V', severity));
 
         let error_code = "29P02";
-        complete_msg.extend(field('C', &error_code));
+        complete_msg.extend(field('C', error_code));
         let message = "password authentication failed for user \"wrong_user\"";
-        complete_msg.extend(field('M', &message));
+        complete_msg.extend(field('M', message));
         let detail_msg = "super detailed message";
-        complete_msg.extend(field('D', &detail_msg));
+        complete_msg.extend(field('D', detail_msg));
         let hint_msg = "hint detail here";
-        complete_msg.extend(field('H', &hint_msg));
+        complete_msg.extend(field('H', hint_msg));
         complete_msg.extend(field('P', "123"));
         complete_msg.extend(field('p', "234"));
         let internal_query = "SELECT * from foo;";
-        complete_msg.extend(field('q', &internal_query));
+        complete_msg.extend(field('q', internal_query));
         let where_msg = "where goes here";
-        complete_msg.extend(field('W', &where_msg));
+        complete_msg.extend(field('W', where_msg));
         let schema_msg = "schema_name";
-        complete_msg.extend(field('s', &schema_msg));
+        complete_msg.extend(field('s', schema_msg));
         let table_msg = "table_name";
-        complete_msg.extend(field('t', &table_msg));
+        complete_msg.extend(field('t', table_msg));
         let column_msg = "column_name";
-        complete_msg.extend(field('c', &column_msg));
+        complete_msg.extend(field('c', column_msg));
         let data_type_msg = "type_name";
-        complete_msg.extend(field('d', &data_type_msg));
+        complete_msg.extend(field('d', data_type_msg));
         let constraint_msg = "constraint_name";
-        complete_msg.extend(field('n', &constraint_msg));
+        complete_msg.extend(field('n', constraint_msg));
         let file_msg = "pgcat.c";
-        complete_msg.extend(field('F', &file_msg));
+        complete_msg.extend(field('F', file_msg));
         complete_msg.extend(field('L', "335"));
         let routine_msg = "my_failing_routine";
-        complete_msg.extend(field('R', &routine_msg));
+        complete_msg.extend(field('R', routine_msg));
 
         tracing_subscriber::fmt()
             .with_max_level(tracing::Level::INFO)
@@ -1351,7 +1478,7 @@ mod tests {
 
         info!(
             "full message: {}",
-            PgErrorMsg::parse(complete_msg.clone()).unwrap()
+            PgErrorMsg::parse(&complete_msg).unwrap()
         );
         assert_eq!(
             PgErrorMsg {
@@ -1374,17 +1501,17 @@ mod tests {
                 line: Some(335),
                 routine: Some(routine_msg.to_string()),
             },
-            PgErrorMsg::parse(complete_msg).unwrap()
+            PgErrorMsg::parse(&complete_msg).unwrap()
         );
 
         let mut only_mandatory_msg = vec![];
-        only_mandatory_msg.extend(field('S', &severity));
-        only_mandatory_msg.extend(field('V', &severity));
-        only_mandatory_msg.extend(field('C', &error_code));
-        only_mandatory_msg.extend(field('M', &message));
-        only_mandatory_msg.extend(field('D', &detail_msg));
+        only_mandatory_msg.extend(field('S', severity));
+        only_mandatory_msg.extend(field('V', severity));
+        only_mandatory_msg.extend(field('C', error_code));
+        only_mandatory_msg.extend(field('M', message));
+        only_mandatory_msg.extend(field('D', detail_msg));
 
-        let err_fields = PgErrorMsg::parse(only_mandatory_msg.clone()).unwrap();
+        let err_fields = PgErrorMsg::parse(&only_mandatory_msg).unwrap();
         info!("only mandatory fields: {}", &err_fields);
         error!(
             "server error: {}: {}",
@@ -1411,7 +1538,7 @@ mod tests {
                 line: None,
                 routine: None,
             },
-            PgErrorMsg::parse(only_mandatory_msg).unwrap()
+            PgErrorMsg::parse(&only_mandatory_msg).unwrap()
         );
     }
 }

src/mirrors.rs

@@ -23,14 +23,15 @@ impl MirroredClient {
     async fn create_pool(&self) -> Pool<ServerPool> {
         let config = get_config();
         let default = std::time::Duration::from_millis(10_000).as_millis() as u64;
-        let (connection_timeout, idle_timeout, _cfg) =
+        let (connection_timeout, idle_timeout, _cfg, prepared_statement_cache_size) =
             match config.pools.get(&self.address.pool_name) {
                 Some(cfg) => (
                     cfg.connect_timeout.unwrap_or(default),
                     cfg.idle_timeout.unwrap_or(default),
                     cfg.clone(),
+                    cfg.prepared_statements_cache_size,
                 ),
-                None => (default, default, crate::config::Pool::default()),
+                None => (default, default, crate::config::Pool::default(), 0),
             };
 
         let manager = ServerPool::new(
@@ -42,6 +43,7 @@ impl MirroredClient {
             None,
             true,
             false,
+            prepared_statement_cache_size,
         );
 
         Pool::builder()
@@ -137,18 +139,18 @@ impl MirroringManager {
                 bytes_rx,
                 disconnect_rx: exit_rx,
             };
-            exit_senders.push(exit_tx.clone());
-            byte_senders.push(bytes_tx.clone());
+            exit_senders.push(exit_tx);
+            byte_senders.push(bytes_tx);
             client.start();
         });
 
         Self {
-            byte_senders: byte_senders,
+            byte_senders,
             disconnect_senders: exit_senders,
         }
     }
 
-    pub fn send(self: &mut Self, bytes: &BytesMut) {
+    pub fn send(&mut self, bytes: &BytesMut) {
         // We want to avoid performing an allocation if we won't be able to send the message
         // There is a possibility of a race here where we check the capacity and then the channel is
         // closed or the capacity is reduced to 0, but mirroring is best effort anyway
@@ -170,7 +172,7 @@ impl MirroringManager {
         });
     }
 
-    pub fn disconnect(self: &mut Self) {
+    pub fn disconnect(&mut self) {
         self.disconnect_senders
             .iter_mut()
             .for_each(|sender| match sender.try_send(()) {

src/plugins/intercept.rs

@@ -92,7 +92,7 @@ impl<'a> Plugin for Intercept<'a> {
                             .map(|s| {
                                 let s = s.as_str().to_string();
 
-                                if s == "" {
+                                if s.is_empty() {
                                     None
                                 } else {
                                     Some(s)

src/plugins/mod.rs

@@ -33,6 +33,7 @@ pub enum PluginOutput {
 #[async_trait]
 pub trait Plugin {
     // Run before the query is sent to the server.
+    #[allow(clippy::ptr_arg)]
     async fn run(
         &mut self,
         query_router: &QueryRouter,

src/plugins/prewarmer.rs

@@ -20,7 +20,7 @@ impl<'a> Prewarmer<'a> {
                 self.server.address(),
                 query
             );
-            self.server.query(&query).await?;
+            self.server.query(query).await?;
         }
 
         Ok(())

src/plugins/table_access.rs

@@ -34,7 +34,7 @@ impl<'a> Plugin for TableAccess<'a> {
 
         visit_relations(ast, |relation| {
             let relation = relation.to_string();
-            let parts = relation.split(".").collect::<Vec<&str>>();
+            let parts = relation.split('.').collect::<Vec<&str>>();
             let table_name = parts.last().unwrap();
 
             if self.tables.contains(&table_name.to_string()) {

src/pool.rs

@@ -3,6 +3,7 @@ use async_trait::async_trait;
 use bb8::{ManageConnection, Pool, PooledConnection, QueueStrategy};
 use chrono::naive::NaiveDateTime;
 use log::{debug, error, info, warn};
+use lru::LruCache;
 use once_cell::sync::Lazy;
 use parking_lot::{Mutex, RwLock};
 use rand::seq::SliceRandom;
@@ -10,6 +11,7 @@ use rand::thread_rng;
 use regex::Regex;
 use std::collections::HashMap;
 use std::fmt::{Display, Formatter};
+use std::num::NonZeroUsize;
 use std::sync::atomic::AtomicU64;
 use std::sync::{
     atomic::{AtomicBool, Ordering},
@@ -24,6 +26,7 @@ use crate::config::{
 use crate::errors::Error;
 
 use crate::auth_passthrough::AuthPassthrough;
+use crate::messages::Parse;
 use crate::plugins::prewarmer;
 use crate::server::{Server, ServerParameters};
 use crate::sharding::ShardingFunction;
@@ -54,6 +57,57 @@ pub enum BanReason {
     AdminBan(i64),
 }
 
+pub type PreparedStatementCacheType = Arc<Mutex<PreparedStatementCache>>;
+
+// TODO: Add stats the this cache
+// TODO: Add application name to the cache value to help identify which application is using the cache
+// TODO: Create admin command to show which statements are in the cache
+#[derive(Debug)]
+pub struct PreparedStatementCache {
+    cache: LruCache<u64, Arc<Parse>>,
+}
+
+impl PreparedStatementCache {
+    pub fn new(mut size: usize) -> Self {
+        // Cannot be zeros
+        if size == 0 {
+            size = 1;
+        }
+
+        PreparedStatementCache {
+            cache: LruCache::new(NonZeroUsize::new(size).unwrap()),
+        }
+    }
+
+    /// Adds the prepared statement to the cache if it doesn't exist with a new name
+    /// if it already exists will give you the existing parse
+    ///
+    /// Pass the hash to this so that we can do the compute before acquiring the lock
+    pub fn get_or_insert(&mut self, parse: &Parse, hash: u64) -> Arc<Parse> {
+        match self.cache.get(&hash) {
+            Some(rewritten_parse) => rewritten_parse.clone(),
+            None => {
+                let new_parse = Arc::new(parse.clone().rewrite());
+                let evicted = self.cache.push(hash, new_parse.clone());
+
+                if let Some((_, evicted_parse)) = evicted {
+                    debug!(
+                        "Evicted prepared statement {} from cache",
+                        evicted_parse.name
+                    );
+                }
+
+                new_parse
+            }
+        }
+    }
+
+    /// Marks the hash as most recently used if it exists
+    pub fn promote(&mut self, hash: &u64) {
+        self.cache.promote(hash);
+    }
+}
+
 /// An identifier for a PgCat pool,
 /// a database visible to clients.
 #[derive(Hash, Debug, Clone, PartialEq, Eq, Default)]
@@ -190,11 +244,11 @@ impl Default for PoolSettings {
 #[derive(Clone, Debug, Default)]
 pub struct ConnectionPool {
     /// The pools handled internally by bb8.
-    databases: Vec<Vec<Pool<ServerPool>>>,
+    databases: Arc<Vec<Vec<Pool<ServerPool>>>>,
 
     /// The addresses (host, port, role) to handle
     /// failover and load balancing deterministically.
-    addresses: Vec<Vec<Address>>,
+    addresses: Arc<Vec<Vec<Address>>>,
 
     /// List of banned addresses (see above)
     /// that should not be queried.
@@ -206,7 +260,7 @@ pub struct ConnectionPool {
     original_server_parameters: Arc<RwLock<ServerParameters>>,
 
     /// Pool configuration.
-    pub settings: PoolSettings,
+    pub settings: Arc<PoolSettings>,
 
     /// If not validated, we need to double check the pool is available before allowing a client
     /// to use it.
@@ -223,6 +277,9 @@ pub struct ConnectionPool {
 
     /// AuthInfo
     pub auth_hash: Arc<RwLock<Option<String>>>,
+
+    /// Cache
+    pub prepared_statement_cache: Option<PreparedStatementCacheType>,
 }
 
 impl ConnectionPool {
@@ -241,20 +298,17 @@ impl ConnectionPool {
                 let old_pool_ref = get_pool(pool_name, &user.username);
                 let identifier = PoolIdentifier::new(pool_name, &user.username);
 
-                match old_pool_ref {
-                    Some(pool) => {
-                        // If the pool hasn't changed, get existing reference and insert it into the new_pools.
-                        // We replace all pools at the end, but if the reference is kept, the pool won't get re-created (bb8).
-                        if pool.config_hash == new_pool_hash_value {
-                            info!(
-                                "[pool: {}][user: {}] has not changed",
-                                pool_name, user.username
-                            );
-                            new_pools.insert(identifier.clone(), pool.clone());
-                            continue;
-                        }
+                if let Some(pool) = old_pool_ref {
+                    // If the pool hasn't changed, get existing reference and insert it into the new_pools.
+                    // We replace all pools at the end, but if the reference is kept, the pool won't get re-created (bb8).
+                    if pool.config_hash == new_pool_hash_value {
+                        info!(
+                            "[pool: {}][user: {}] has not changed",
+                            pool_name, user.username
+                        );
+                        new_pools.insert(identifier.clone(), pool.clone());
+                        continue;
                     }
-                    None => (),
                 }
 
                 info!(
@@ -379,16 +433,23 @@ impl ConnectionPool {
                             },
                             pool_config.cleanup_server_connections,
                             pool_config.log_client_parameter_status_changes,
+                            pool_config.prepared_statements_cache_size,
                         );
 
-                        let connect_timeout = match pool_config.connect_timeout {
+                        let connect_timeout = match user.connect_timeout {
                             Some(connect_timeout) => connect_timeout,
-                            None => config.general.connect_timeout,
+                            None => match pool_config.connect_timeout {
+                                Some(connect_timeout) => connect_timeout,
+                                None => config.general.connect_timeout,
+                            },
                         };
 
-                        let idle_timeout = match pool_config.idle_timeout {
+                        let idle_timeout = match user.idle_timeout {
                             Some(idle_timeout) => idle_timeout,
-                            None => config.general.idle_timeout,
+                            None => match pool_config.idle_timeout {
+                                Some(idle_timeout) => idle_timeout,
+                                None => config.general.idle_timeout,
+                            },
                         };
 
                         let server_lifetime = match user.server_lifetime {
@@ -399,7 +460,7 @@ impl ConnectionPool {
                             },
                         };
 
-                        let reaper_rate = *vec![idle_timeout, server_lifetime, POOL_REAPER_RATE]
+                        let reaper_rate = *[idle_timeout, server_lifetime, POOL_REAPER_RATE]
                             .iter()
                             .min()
                             .unwrap();
@@ -448,13 +509,13 @@ impl ConnectionPool {
                 }
 
                 let pool = ConnectionPool {
-                    databases: shards,
-                    addresses,
+                    databases: Arc::new(shards),
+                    addresses: Arc::new(addresses),
                     banlist: Arc::new(RwLock::new(banlist)),
                     config_hash: new_pool_hash_value,
                     original_server_parameters: Arc::new(RwLock::new(ServerParameters::new())),
                     auth_hash: pool_auth_hash,
-                    settings: PoolSettings {
+                    settings: Arc::new(PoolSettings {
                         pool_mode: match user.pool_mode {
                             Some(pool_mode) => pool_mode,
                             None => pool_config.pool_mode,
@@ -489,7 +550,7 @@ impl ConnectionPool {
                             .clone()
                             .map(|regex| Regex::new(regex.as_str()).unwrap()),
                         regex_search_limit: pool_config.regex_search_limit.unwrap_or(1000),
-                        default_shard: pool_config.default_shard.clone(),
+                        default_shard: pool_config.default_shard,
                         auth_query: pool_config.auth_query.clone(),
                         auth_query_user: pool_config.auth_query_user.clone(),
                         auth_query_password: pool_config.auth_query_password.clone(),
@@ -497,17 +558,23 @@ impl ConnectionPool {
                             Some(ref plugins) => Some(plugins.clone()),
                             None => config.plugins.clone(),
                         },
-                    },
+                    }),
                     validated: Arc::new(AtomicBool::new(false)),
                     paused: Arc::new(AtomicBool::new(false)),
                     paused_waiter: Arc::new(Notify::new()),
+                    prepared_statement_cache: match pool_config.prepared_statements_cache_size {
+                        0 => None,
+                        _ => Some(Arc::new(Mutex::new(PreparedStatementCache::new(
+                            pool_config.prepared_statements_cache_size,
+                        )))),
+                    },
                 };
 
                 // Connect to the servers to make sure pool configuration is valid
                 // before setting it globally.
                 // Do this async and somewhere else, we don't have to wait here.
                 if config.general.validate_config {
-                    let mut validate_pool = pool.clone();
+                    let validate_pool = pool.clone();
                     tokio::task::spawn(async move {
                         let _ = validate_pool.validate().await;
                     });
@@ -528,7 +595,7 @@ impl ConnectionPool {
     /// when they connect.
     /// This also warms up the pool for clients that connect when
     /// the pooler starts up.
-    pub async fn validate(&mut self) -> Result<(), Error> {
+    pub async fn validate(&self) -> Result<(), Error> {
         let mut futures = Vec::new();
         let validated = Arc::clone(&self.validated);
 
@@ -678,7 +745,7 @@ impl ConnectionPool {
             let mut force_healthcheck = false;
 
             if self.is_banned(address) {
-                if self.try_unban(&address).await {
+                if self.try_unban(address).await {
                     force_healthcheck = true;
                 } else {
                     debug!("Address {:?} is banned", address);
@@ -806,8 +873,8 @@ impl ConnectionPool {
         // Don't leave a bad connection in the pool.
         server.mark_bad();
 
-        self.ban(&address, BanReason::FailedHealthCheck, Some(client_info));
-        return false;
+        self.ban(address, BanReason::FailedHealthCheck, Some(client_info));
+        false
     }
 
     /// Ban an address (i.e. replica). It no longer will serve
@@ -931,10 +998,10 @@ impl ConnectionPool {
         let guard = self.banlist.read();
         for banlist in guard.iter() {
             for (address, (reason, timestamp)) in banlist.iter() {
-                bans.push((address.clone(), (reason.clone(), timestamp.clone())));
+                bans.push((address.clone(), (reason.clone(), *timestamp)));
             }
         }
-        return bans;
+        bans
     }
 
     /// Get the address from the host url
@@ -992,7 +1059,7 @@ impl ConnectionPool {
         }
         let busy = provisioned - idle;
         debug!("{:?} has {:?} busy connections", address, busy);
-        return busy;
+        busy
     }
 
     fn valid_shard_id(&self, shard: Option<usize>) -> bool {
@@ -1001,6 +1068,29 @@ impl ConnectionPool {
             Some(shard) => shard < self.shards(),
         }
     }
+
+    /// Register a parse statement to the pool's cache and return the rewritten parse
+    ///
+    /// Do not pass an anonymous parse statement to this function
+    pub fn register_parse_to_cache(&self, hash: u64, parse: &Parse) -> Option<Arc<Parse>> {
+        // We should only be calling this function if the cache is enabled
+        match self.prepared_statement_cache {
+            Some(ref prepared_statement_cache) => {
+                let mut cache = prepared_statement_cache.lock();
+                Some(cache.get_or_insert(parse, hash))
+            }
+            None => None,
+        }
+    }
+
+    /// Promote a prepared statement hash in the LRU
+    pub fn promote_prepared_statement_hash(&self, hash: &u64) {
+        // We should only be calling this function if the cache is enabled
+        if let Some(ref prepared_statement_cache) = self.prepared_statement_cache {
+            let mut cache = prepared_statement_cache.lock();
+            cache.promote(hash);
+        }
+    }
 }
 
 /// Wrapper for the bb8 connection pool.
@@ -1028,9 +1118,13 @@ pub struct ServerPool {
 
     /// Log client parameter status changes
     log_client_parameter_status_changes: bool,
+
+    /// Prepared statement cache size
+    prepared_statement_cache_size: usize,
 }
 
 impl ServerPool {
+    #[allow(clippy::too_many_arguments)]
     pub fn new(
         address: Address,
         user: User,
@@ -1040,16 +1134,18 @@ impl ServerPool {
         plugins: Option<Plugins>,
         cleanup_connections: bool,
         log_client_parameter_status_changes: bool,
+        prepared_statement_cache_size: usize,
     ) -> ServerPool {
         ServerPool {
             address,
-            user: user.clone(),
+            user,
             database: database.to_string(),
             client_server_map,
             auth_hash,
             plugins,
             cleanup_connections,
             log_client_parameter_status_changes,
+            prepared_statement_cache_size,
         }
     }
 }
@@ -1080,6 +1176,7 @@ impl ManageConnection for ServerPool {
             self.auth_hash.clone(),
             self.cleanup_connections,
             self.log_client_parameter_status_changes,
+            self.prepared_statement_cache_size,
         )
         .await
         {

src/query_router.rs

@@ -4,10 +4,10 @@ use bytes::{Buf, BytesMut};
 use log::{debug, error};
 use once_cell::sync::OnceCell;
 use regex::{Regex, RegexSet};
-use sqlparser::ast::Statement::{Query, StartTransaction};
+use sqlparser::ast::Statement::{Delete, Insert, Query, StartTransaction, Update};
 use sqlparser::ast::{
-    BinaryOperator, Expr, Ident, JoinConstraint, JoinOperator, SetExpr, Statement, TableFactor,
-    Value,
+    Assignment, BinaryOperator, Expr, Ident, JoinConstraint, JoinOperator, SetExpr, Statement,
+    TableFactor, TableWithJoins, Value,
 };
 use sqlparser::dialect::PostgreSqlDialect;
 use sqlparser::parser::Parser;
@@ -91,7 +91,7 @@ impl QueryRouter {
     /// One-time initialization of regexes
     /// that parse our custom SQL protocol.
     pub fn setup() -> bool {
-        let set = match RegexSet::new(&CUSTOM_SQL_REGEXES) {
+        let set = match RegexSet::new(CUSTOM_SQL_REGEXES) {
             Ok(rgx) => rgx,
             Err(err) => {
                 error!("QueryRouter::setup Could not compile regex set: {:?}", err);
@@ -128,11 +128,11 @@ impl QueryRouter {
     }
 
     /// Pool settings can change because of a config reload.
-    pub fn update_pool_settings(&mut self, pool_settings: PoolSettings) {
-        self.pool_settings = pool_settings;
+    pub fn update_pool_settings(&mut self, pool_settings: &PoolSettings) {
+        self.pool_settings = pool_settings.clone();
     }
 
-    pub fn pool_settings<'a>(&'a self) -> &'a PoolSettings {
+    pub fn pool_settings(&self) -> &PoolSettings {
         &self.pool_settings
     }
 
@@ -148,7 +148,7 @@ impl QueryRouter {
 
         // Check for any sharding regex matches in any queries
         if comment_shard_routing_enabled {
-            match code as char {
+            match code {
                 // For Parse and Query messages peek to see if they specify a shard_id as a comment early in the statement
                 'P' | 'Q' => {
                     // Check only the first block of bytes configured by the pool settings
@@ -344,16 +344,13 @@ impl QueryRouter {
         let code = message_cursor.get_u8() as char;
         let len = message_cursor.get_i32() as usize;
 
-        match self.pool_settings.query_parser_max_length {
-            Some(max_length) => {
-                if len > max_length {
-                    return Err(Error::QueryRouterParserError(format!(
-                        "Query too long for parser: {} > {}",
-                        len, max_length
-                    )));
-                }
+        if let Some(max_length) = self.pool_settings.query_parser_max_length {
+            if len > max_length {
+                return Err(Error::QueryRouterParserError(format!(
+                    "Query too long for parser: {} > {}",
+                    len, max_length
+                )));
             }
-            None => (),
         };
 
         let query = match code {
@@ -403,6 +400,9 @@ impl QueryRouter {
             return Err(Error::QueryRouterParserError("empty query".into()));
         }
 
+        let mut visited_write_statement = false;
+        let mut prev_inferred_shard = None;
+
         for q in ast {
             match q {
                 // All transactions go to the primary, probably a write.
@@ -420,29 +420,38 @@ impl QueryRouter {
                             // or discard shard selection. If they point to the same shard though,
                             // we can let them through as-is.
                             // This is basically building a database now :)
-                            match self.infer_shard(query) {
-                                Some(shard) => {
-                                    self.active_shard = Some(shard);
-                                    debug!("Automatically using shard: {:?}", self.active_shard);
-                                }
-
-                                None => (),
-                            };
+                            let inferred_shard = self.infer_shard(query);
+                            self.handle_inferred_shard(inferred_shard, &mut prev_inferred_shard)?;
                         }
 
                         None => (),
                     };
 
-                    self.active_role = match self.primary_reads_enabled() {
-                        false => Some(Role::Replica), // If primary should not be receiving reads, use a replica.
-                        true => None,                 // Any server role is fine in this case.
+                    // If we already visited a write statement, we should be going to the primary.
+                    if !visited_write_statement {
+                        self.active_role = match self.primary_reads_enabled() {
+                            false => Some(Role::Replica), // If primary should not be receiving reads, use a replica.
+                            true => None,                 // Any server role is fine in this case.
+                        }
                     }
                 }
 
                 // Likely a write
                 _ => {
+                    match &self.pool_settings.automatic_sharding_key {
+                        Some(_) => {
+                            // TODO: similar to the above, if we have multiple queries in the
+                            // same message, we can either split them and execute them individually
+                            // or discard shard selection. If they point to the same shard though,
+                            // we can let them through as-is.
+                            let inferred_shard = self.infer_shard_on_write(q)?;
+                            self.handle_inferred_shard(inferred_shard, &mut prev_inferred_shard)?;
+                        }
+
+                        None => (),
+                    };
+                    visited_write_statement = true;
                     self.active_role = Some(Role::Primary);
-                    break;
                 }
             };
         }
@@ -450,6 +459,188 @@ impl QueryRouter {
         Ok(())
     }
 
+    fn handle_inferred_shard(
+        &mut self,
+        inferred_shard: Option<usize>,
+        prev_inferred_shard: &mut Option<usize>,
+    ) -> Result<(), Error> {
+        if let Some(shard) = inferred_shard {
+            if let Some(prev_shard) = *prev_inferred_shard {
+                if prev_shard != shard {
+                    debug!("Found more than one shard in the query, not supported yet");
+                    return Err(Error::QueryRouterParserError(
+                        "multiple shards in query".into(),
+                    ));
+                }
+            }
+            *prev_inferred_shard = Some(shard);
+            self.active_shard = Some(shard);
+            debug!("Automatically using shard: {:?}", self.active_shard);
+        };
+        Ok(())
+    }
+
+    fn infer_shard_on_write(&mut self, q: &Statement) -> Result<Option<usize>, Error> {
+        let mut exprs = Vec::new();
+
+        // Collect all table names from the query.
+        let mut table_names = Vec::new();
+
+        match q {
+            Insert {
+                or,
+                into: _,
+                table_name,
+                columns,
+                overwrite: _,
+                source,
+                partitioned,
+                after_columns,
+                table: _,
+                on: _,
+                returning: _,
+            } => {
+                // Not supported in postgres.
+                assert!(or.is_none());
+                assert!(partitioned.is_none());
+                assert!(after_columns.is_empty());
+
+                Self::process_table(table_name, &mut table_names);
+                Self::process_query(source, &mut exprs, &mut table_names, &Some(columns));
+            }
+            Delete {
+                tables,
+                from,
+                using,
+                selection,
+                returning: _,
+            } => {
+                if let Some(expr) = selection {
+                    exprs.push(expr.clone());
+                }
+
+                // Multi tables delete are not supported in postgres.
+                assert!(tables.is_empty());
+
+                Self::process_tables_with_join(from, &mut exprs, &mut table_names);
+                if let Some(using_tbl_with_join) = using {
+                    Self::process_tables_with_join(
+                        using_tbl_with_join,
+                        &mut exprs,
+                        &mut table_names,
+                    );
+                }
+                Self::process_selection(selection, &mut exprs);
+            }
+            Update {
+                table,
+                assignments,
+                from,
+                selection,
+                returning: _,
+            } => {
+                Self::process_table_with_join(table, &mut exprs, &mut table_names);
+                if let Some(from_tbl) = from {
+                    Self::process_table_with_join(from_tbl, &mut exprs, &mut table_names);
+                }
+                Self::process_selection(selection, &mut exprs);
+                self.assignment_parser(assignments)?;
+            }
+            _ => {
+                return Ok(None);
+            }
+        };
+
+        Ok(self.infer_shard_from_exprs(exprs, table_names))
+    }
+
+    fn process_query(
+        query: &sqlparser::ast::Query,
+        exprs: &mut Vec<Expr>,
+        table_names: &mut Vec<Vec<Ident>>,
+        columns: &Option<&Vec<Ident>>,
+    ) {
+        match &*query.body {
+            SetExpr::Query(query) => {
+                Self::process_query(query, exprs, table_names, columns);
+            }
+
+            // SELECT * FROM ...
+            // We understand that pretty well.
+            SetExpr::Select(select) => {
+                Self::process_tables_with_join(&select.from, exprs, table_names);
+
+                // Parse the actual "FROM ..."
+                Self::process_selection(&select.selection, exprs);
+            }
+
+            SetExpr::Values(values) => {
+                if let Some(cols) = columns {
+                    for row in values.rows.iter() {
+                        for (i, expr) in row.iter().enumerate() {
+                            if cols.len() > i {
+                                exprs.push(Expr::BinaryOp {
+                                    left: Box::new(Expr::Identifier(cols[i].clone())),
+                                    op: BinaryOperator::Eq,
+                                    right: Box::new(expr.clone()),
+                                });
+                            }
+                        }
+                    }
+                }
+            }
+            _ => (),
+        };
+    }
+
+    fn process_selection(selection: &Option<Expr>, exprs: &mut Vec<Expr>) {
+        match selection {
+            Some(selection) => {
+                exprs.push(selection.clone());
+            }
+
+            None => (),
+        };
+    }
+
+    fn process_tables_with_join(
+        tables: &[TableWithJoins],
+        exprs: &mut Vec<Expr>,
+        table_names: &mut Vec<Vec<Ident>>,
+    ) {
+        for table in tables.iter() {
+            Self::process_table_with_join(table, exprs, table_names);
+        }
+    }
+
+    fn process_table_with_join(
+        table: &TableWithJoins,
+        exprs: &mut Vec<Expr>,
+        table_names: &mut Vec<Vec<Ident>>,
+    ) {
+        if let TableFactor::Table { name, .. } = &table.relation {
+            Self::process_table(name, table_names);
+        };
+
+        // Get table names from all the joins.
+        for join in table.joins.iter() {
+            if let TableFactor::Table { name, .. } = &join.relation {
+                Self::process_table(name, table_names);
+            };
+
+            // We can filter results based on join conditions, e.g.
+            // SELECT * FROM t INNER JOIN B ON B.sharding_key = 5;
+            if let JoinOperator::Inner(JoinConstraint::On(expr)) = &join.join_operator {
+                // Parse the selection criteria later.
+                exprs.push(expr.clone());
+            };
+        }
+    }
+
+    fn process_table(name: &sqlparser::ast::ObjectName, table_names: &mut Vec<Vec<Ident>>) {
+        table_names.push(name.0.clone())
+    }
+
     /// Parse the shard number from the Bind message
     /// which contains the arguments for a prepared statement.
     ///
@@ -592,6 +783,33 @@ impl QueryRouter {
         }
     }
 
+    /// An `assignments` exists in the `UPDATE` statements. This parses the assignments and makes
+    /// sure that we are not updating the sharding key. It's not supported yet.
+    fn assignment_parser(&self, assignments: &Vec<Assignment>) -> Result<(), Error> {
+        let sharding_key = self
+            .pool_settings
+            .automatic_sharding_key
+            .as_ref()
+            .unwrap()
+            .split('.')
+            .map(|ident| Ident::new(ident.to_lowercase()))
+            .collect::<Vec<Ident>>();
+
+        // Sharding key must be always fully qualified
+        assert_eq!(sharding_key.len(), 2);
+
+        for a in assignments {
+            if sharding_key[0].value == "*"
+                && sharding_key[1].value == a.id.last().unwrap().value.to_lowercase()
+            {
+                return Err(Error::QueryRouterParserError(
+                    "Sharding key cannot be updated.".into(),
+                ));
+            }
+        }
+        Ok(())
+    }
+
     /// A `selection` is the `WHERE` clause. This parses
     /// the clause and extracts the sharding key, if present.
     fn selection_parser(&self, expr: &Expr, table_names: &Vec<Vec<Ident>>) -> Vec<ShardingKey> {
@@ -603,8 +821,8 @@ impl QueryRouter {
             .automatic_sharding_key
             .as_ref()
             .unwrap()
-            .split(".")
-            .map(|ident| Ident::new(ident))
+            .split('.')
+            .map(|ident| Ident::new(ident.to_lowercase()))
             .collect::<Vec<Ident>>();
 
         // Sharding key must be always fully qualified
@@ -620,7 +838,7 @@ impl QueryRouter {
                 Expr::Identifier(ident) => {
                     // Only if we're dealing with only one table
                     // and there is no ambiguity
-                    if &ident.value == &sharding_key[1].value {
+                    if ident.value.to_lowercase() == sharding_key[1].value {
                         // Sharding key is unique enough, don't worry about
                         // table names.
                         if &sharding_key[0].value == "*" {
@@ -633,13 +851,13 @@ impl QueryRouter {
                                 //      SELECT * FROM t WHERE sharding_key = 5
                                 // Make sure the table name from the sharding key matches
                                 // the table name from the query.
-                                found = &sharding_key[0].value == &table[0].value;
+                                found = sharding_key[0].value == table[0].value.to_lowercase();
                             } else if table.len() == 2 {
                                 // Table name is fully qualified with the schema: e.g.
                                 //      SELECT * FROM public.t WHERE sharding_key = 5
                                 // Ignore the schema (TODO: at some point, we want schema support)
                                 // and use the table name only.
-                                found = &sharding_key[0].value == &table[1].value;
+                                found = sharding_key[0].value == table[1].value.to_lowercase();
                             } else {
                                 debug!("Got table name with more than two idents, which is not possible");
                             }
@@ -651,8 +869,9 @@ impl QueryRouter {
                     // The key is fully qualified in the query,
                     // it will exist or Postgres will throw an error.
                     if idents.len() == 2 {
-                        found = &sharding_key[0].value == &idents[0].value
-                            && &sharding_key[1].value == &idents[1].value;
+                        found = (&sharding_key[0].value == "*"
+                            || sharding_key[0].value == idents[0].value.to_lowercase())
+                            && sharding_key[1].value == idents[1].value.to_lowercase();
                     }
                     // TODO: key can have schema as well, e.g. public.data.id (len == 3)
                 }
@@ -684,7 +903,7 @@ impl QueryRouter {
                 }
 
                 Expr::Value(Value::Placeholder(placeholder)) => {
-                    match placeholder.replace("$", "").parse::<i16>() {
+                    match placeholder.replace('$', "").parse::<i16>() {
                         Ok(placeholder) => result.push(ShardingKey::Placeholder(placeholder)),
                         Err(_) => {
                             debug!(
@@ -705,100 +924,48 @@ impl QueryRouter {
 
     /// Try to figure out which shard the query should go to.
     fn infer_shard(&mut self, query: &sqlparser::ast::Query) -> Option<usize> {
-        let mut shards = BTreeSet::new();
         let mut exprs = Vec::new();
 
-        match &*query.body {
-            SetExpr::Query(query) => {
-                match self.infer_shard(&*query) {
-                    Some(shard) => {
+        // Collect all table names from the query.
+        let mut table_names = Vec::new();
+
+        Self::process_query(query, &mut exprs, &mut table_names, &None);
+        self.infer_shard_from_exprs(exprs, table_names)
+    }
+
+    fn infer_shard_from_exprs(
+        &mut self,
+        exprs: Vec<Expr>,
+        table_names: Vec<Vec<Ident>>,
+    ) -> Option<usize> {
+        let mut shards = BTreeSet::new();
+
+        let sharder = Sharder::new(
+            self.pool_settings.shards,
+            self.pool_settings.sharding_function,
+        );
+
+        // Look for sharding keys in either the join condition
+        // or the selection.
+        for expr in exprs.iter() {
+            let sharding_keys = self.selection_parser(expr, &table_names);
+
+            // TODO: Add support for prepared statements here.
+            // This should just give us the position of the value in the `B` message.
+
+            for value in sharding_keys {
+                match value {
+                    ShardingKey::Value(value) => {
+                        let shard = sharder.shard(value);
                         shards.insert(shard);
                     }
-                    None => (),
+
+                    ShardingKey::Placeholder(position) => {
+                        self.placeholders.push(position);
+                    }
                 };
             }
-
-            // SELECT * FROM ...
-            // We understand that pretty well.
-            SetExpr::Select(select) => {
-                // Collect all table names from the query.
-                let mut table_names = Vec::new();
-
-                for table in select.from.iter() {
-                    match &table.relation {
-                        TableFactor::Table { name, .. } => {
-                            table_names.push(name.0.clone());
-                        }
-
-                        _ => (),
-                    };
-
-                    // Get table names from all the joins.
-                    for join in table.joins.iter() {
-                        match &join.relation {
-                            TableFactor::Table { name, .. } => {
-                                table_names.push(name.0.clone());
-                            }
-
-                            _ => (),
-                        };
-
-                        // We can filter results based on join conditions, e.g.
-                        // SELECT * FROM t INNER JOIN B ON B.sharding_key = 5;
-                        match &join.join_operator {
-                            JoinOperator::Inner(inner_join) => match &inner_join {
-                                JoinConstraint::On(expr) => {
-                                    // Parse the selection criteria later.
-                                    exprs.push(expr.clone());
-                                }
-
-                                _ => (),
-                            },
-
-                            _ => (),
-                        };
-                    }
-                }
-
-                // Parse the actual "FROM ..."
-                match &select.selection {
-                    Some(selection) => {
-                        exprs.push(selection.clone());
-                    }
-
-                    None => (),
-                };
-
-                let sharder = Sharder::new(
-                    self.pool_settings.shards,
-                    self.pool_settings.sharding_function,
-                );
-
-                // Look for sharding keys in either the join condition
-                // or the selection.
-                for expr in exprs.iter() {
-                    let sharding_keys = self.selection_parser(expr, &table_names);
-
-                    // TODO: Add support for prepared statements here.
-                    // This should just give us the position of the value in the `B` message.
-
-                    for value in sharding_keys {
-                        match value {
-                            ShardingKey::Value(value) => {
-                                let shard = sharder.shard(value);
-                                shards.insert(shard);
-                            }
-
-                            ShardingKey::Placeholder(position) => {
-                                self.placeholders.push(position);
-                            }
-                        };
-                    }
-                }
-            }
-            _ => (),
-        };
-
+        }
         match shards.len() {
             // Didn't find a sharding key, you're on your own.
             0 => {
@@ -830,16 +997,16 @@ impl QueryRouter {
                 db: &self.pool_settings.db,
             };
 
-            let _ = query_logger.run(&self, ast).await;
+            let _ = query_logger.run(self, ast).await;
         }
 
         if let Some(ref intercept) = plugins.intercept {
             let mut intercept = Intercept {
                 enabled: intercept.enabled,
-                config: &intercept,
+                config: intercept,
             };
 
-            let result = intercept.run(&self, ast).await;
+            let result = intercept.run(self, ast).await;
 
             if let Ok(PluginOutput::Intercept(output)) = result {
                 return Ok(PluginOutput::Intercept(output));
@@ -852,7 +1019,7 @@ impl QueryRouter {
                 tables: &table_access.tables,
             };
 
-            let result = table_access.run(&self, ast).await;
+            let result = table_access.run(self, ast).await;
 
             if let Ok(PluginOutput::Deny(error)) = result {
                 return Ok(PluginOutput::Deny(error));
@@ -888,7 +1055,7 @@ impl QueryRouter {
 
     /// Should we attempt to parse queries?
     pub fn query_parser_enabled(&self) -> bool {
-        let enabled = match self.query_parser_enabled {
+        match self.query_parser_enabled {
             None => {
                 debug!(
                     "Using pool settings, query_parser_enabled: {}",
@@ -904,9 +1071,7 @@ impl QueryRouter {
                 );
                 value
             }
-        };
-
-        enabled
+        }
     }
 
     pub fn primary_reads_enabled(&self) -> bool {
@@ -917,6 +1082,12 @@ impl QueryRouter {
     }
 }
 
+impl Default for QueryRouter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
@@ -938,10 +1109,14 @@ mod test {
         QueryRouter::setup();
         let mut qr = QueryRouter::new();
         qr.pool_settings.query_parser_read_write_splitting = true;
-        assert!(qr.try_execute_command(&simple_query("SET SERVER ROLE TO 'auto'")) != None);
+        assert!(qr
+            .try_execute_command(&simple_query("SET SERVER ROLE TO 'auto'"))
+            .is_some());
         assert!(qr.query_parser_enabled());
 
-        assert!(qr.try_execute_command(&simple_query("SET PRIMARY READS TO off")) != None);
+        assert!(qr
+            .try_execute_command(&simple_query("SET PRIMARY READS TO off"))
+            .is_some());
 
         let queries = vec![
             simple_query("SELECT * FROM items WHERE id = 5"),
@@ -983,7 +1158,9 @@ mod test {
         QueryRouter::setup();
         let mut qr = QueryRouter::new();
         let query = simple_query("SELECT * FROM items WHERE id = 5");
-        assert!(qr.try_execute_command(&simple_query("SET PRIMARY READS TO on")) != None);
+        assert!(qr
+            .try_execute_command(&simple_query("SET PRIMARY READS TO on"))
+            .is_some());
 
         assert!(qr.infer(&qr.parse(&query).unwrap()).is_ok());
         assert_eq!(qr.role(), None);
@@ -996,7 +1173,9 @@ mod test {
         qr.pool_settings.query_parser_read_write_splitting = true;
 
         qr.try_execute_command(&simple_query("SET SERVER ROLE TO 'auto'"));
-        assert!(qr.try_execute_command(&simple_query("SET PRIMARY READS TO off")) != None);
+        assert!(qr
+            .try_execute_command(&simple_query("SET PRIMARY READS TO off"))
+            .is_some());
 
         let prepared_stmt = BytesMut::from(
             &b"WITH t AS (SELECT * FROM items WHERE name = $1) SELECT * FROM t WHERE id = $2\0"[..],
@@ -1166,9 +1345,11 @@ mod test {
         qr.pool_settings.query_parser_read_write_splitting = true;
 
         let query = simple_query("SET SERVER ROLE TO 'auto'");
-        assert!(qr.try_execute_command(&simple_query("SET PRIMARY READS TO off")) != None);
+        assert!(qr
+            .try_execute_command(&simple_query("SET PRIMARY READS TO off"))
+            .is_some());
 
-        assert!(qr.try_execute_command(&query) != None);
+        assert!(qr.try_execute_command(&query).is_some());
         assert!(qr.query_parser_enabled());
         assert_eq!(qr.role(), None);
 
@@ -1182,7 +1363,7 @@ mod test {
 
         assert!(qr.query_parser_enabled());
         let query = simple_query("SET SERVER ROLE TO 'default'");
-        assert!(qr.try_execute_command(&query) != None);
+        assert!(qr.try_execute_command(&query).is_some());
         assert!(!qr.query_parser_enabled());
     }
 
@@ -1222,7 +1403,7 @@ mod test {
         assert_eq!(qr.primary_reads_enabled, None);
 
         // Internal state must not be changed due to this, only defaults
-        qr.update_pool_settings(pool_settings.clone());
+        qr.update_pool_settings(&pool_settings);
 
         assert_eq!(qr.active_role, None);
         assert_eq!(qr.active_shard, None);
@@ -1230,11 +1411,11 @@ mod test {
         assert!(!qr.primary_reads_enabled());
 
         let q1 = simple_query("SET SERVER ROLE TO 'primary'");
-        assert!(qr.try_execute_command(&q1) != None);
+        assert!(qr.try_execute_command(&q1).is_some());
         assert_eq!(qr.active_role.unwrap(), Role::Primary);
 
         let q2 = simple_query("SET SERVER ROLE TO 'default'");
-        assert!(qr.try_execute_command(&q2) != None);
+        assert!(qr.try_execute_command(&q2).is_some());
         assert_eq!(qr.active_role.unwrap(), pool_settings.default_role);
     }
 
@@ -1295,29 +1476,29 @@ mod test {
         };
 
         let mut qr = QueryRouter::new();
-        qr.update_pool_settings(pool_settings.clone());
+        qr.update_pool_settings(&pool_settings);
 
         // Shard should start out unset
         assert_eq!(qr.active_shard, None);
 
         // Don't panic when short query eg. ; is sent
         let q0 = simple_query(";");
-        assert!(qr.try_execute_command(&q0) == None);
+        assert!(qr.try_execute_command(&q0).is_none());
         assert_eq!(qr.active_shard, None);
 
         // Make sure setting it works
         let q1 = simple_query("/* shard_id: 1 */ select 1 from foo;");
-        assert!(qr.try_execute_command(&q1) == None);
+        assert!(qr.try_execute_command(&q1).is_none());
         assert_eq!(qr.active_shard, Some(1));
 
         // And make sure changing it works
         let q2 = simple_query("/* shard_id: 0 */ select 1 from foo;");
-        assert!(qr.try_execute_command(&q2) == None);
+        assert!(qr.try_execute_command(&q2).is_none());
         assert_eq!(qr.active_shard, Some(0));
 
         // Validate setting by shard with expected shard copied from sharding.rs tests
         let q2 = simple_query("/* sharding_key: 6 */ select 1 from foo;");
-        assert!(qr.try_execute_command(&q2) == None);
+        assert!(qr.try_execute_command(&q2).is_none());
         assert_eq!(qr.active_shard, Some(2));
     }
 
@@ -1414,6 +1595,221 @@ mod test {
         assert_eq!(qr.shard().unwrap(), 0);
     }
 
+    fn auto_shard_wrapper(qry: &str, should_succeed: bool) -> Option<usize> {
+        let mut qr = QueryRouter::new();
+        qr.pool_settings.automatic_sharding_key = Some("*.w_id".to_string());
+        qr.pool_settings.shards = 3;
+        qr.pool_settings.query_parser_read_write_splitting = true;
+        assert_eq!(qr.shard(), None);
+        let infer_res = qr.infer(&qr.parse(&simple_query(qry)).unwrap());
+        assert_eq!(infer_res.is_ok(), should_succeed);
+        qr.shard()
+    }
+
+    fn auto_shard(qry: &str) -> Option<usize> {
+        auto_shard_wrapper(qry, true)
+    }
+
+    fn auto_shard_fails(qry: &str) -> Option<usize> {
+        auto_shard_wrapper(qry, false)
+    }
+
+    #[test]
+    fn test_automatic_sharding_insert_update_delete() {
+        QueryRouter::setup();
+
+        assert_eq!(
+            auto_shard_fails(
+                "UPDATE ORDERS SET w_id = 3 WHERE O_ID = 3 AND O_D_ID = 3 AND W_ID = 5"
+            ),
+            None
+        );
+
+        assert_eq!(
+            auto_shard_fails(
+                "UPDATE ORDERS o SET o.W_ID = 3 WHERE o.O_ID = 3 AND o.O_D_ID = 3 AND o.W_ID = 5"
+            ),
+            None
+        );
+
+        assert_eq!(
+            auto_shard(
+                "UPDATE ORDERS o SET o.O_CARRIER_ID = 3 WHERE o.O_ID = 3 AND o.O_D_ID = 3 AND o.W_ID = 5"
+            ),
+            Some(2)
+        );
+    }
+
+    #[test]
+    fn test_automatic_sharding_key_tpcc() {
+        QueryRouter::setup();
+
+        assert_eq!(auto_shard("SELECT * FROM my_tbl WHERE w_id = 5"), Some(2));
+        assert_eq!(
+            auto_shard("BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ"),
+            None
+        );
+        assert_eq!(auto_shard("COMMIT"), None);
+        assert_eq!(auto_shard("ROLLBACK"), None);
+
+        assert_eq!(auto_shard("SELECT NO_O_ID FROM NEW_ORDER WHERE NO_D_ID = 7 AND W_ID = 5 AND NO_O_ID > 3 LIMIT 3"), Some(2));
+        assert_eq!(auto_shard("SELECT NO_O_ID FROM NEW_ORDER no WHERE no.NO_D_ID = 7 AND no.W_ID = 5 AND no.NO_O_ID > 3 LIMIT 3"), Some(2));
+
+        assert_eq!(
+            auto_shard("DELETE FROM NEW_ORDER WHERE NO_D_ID = 7 AND W_ID = 5 AND NO_O_ID = 3"),
+            Some(2)
+        );
+
+        assert_eq!(
+            auto_shard("SELECT O_C_ID FROM ORDERS WHERE O_ID = 3 AND O_D_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard(
+                "UPDATE ORDERS SET O_CARRIER_ID = 3 WHERE O_ID = 3 AND O_D_ID = 3 AND W_ID = 5"
+            ),
+            Some(2)
+        );
+
+        assert_eq!(
+            auto_shard("UPDATE ORDER_LINE SET OL_DELIVERY_D = 3 WHERE OL_O_ID = 3 AND OL_D_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+
+        assert_eq!(
+            auto_shard("SELECT SUM(OL_AMOUNT) FROM ORDER_LINE WHERE OL_O_ID = 3 AND OL_D_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+
+        assert_eq!(
+            auto_shard("UPDATE CUSTOMER SET C_BALANCE = C_BALANCE + 3 WHERE C_ID = 3 AND C_D_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+
+        assert_eq!(
+            auto_shard("SELECT W_TAX FROM WAREHOUSE WHERE W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT D_TAX, D_NEXT_O_ID FROM DISTRICT WHERE D_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("UPDATE DISTRICT SET D_NEXT_O_ID = 3 WHERE D_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT C_DISCOUNT, C_LAST, C_CREDIT FROM CUSTOMER WHERE W_ID = 5 AND C_D_ID = 3 AND C_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("INSERT INTO ORDERS (O_ID, O_D_ID, W_ID, O_C_ID, O_ENTRY_D, O_CARRIER_ID, O_OL_CNT, O_ALL_LOCAL) VALUES (3, 3, 5, 3, 3, 3, 3, 3)"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("INSERT INTO NEW_ORDER (NO_O_ID, NO_D_ID, W_ID) VALUES (3, 3, 5)"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT I_PRICE, I_NAME, I_DATA FROM ITEM WHERE I_ID = 3"),
+            None
+        );
+        assert_eq!(
+            auto_shard("SELECT S_QUANTITY, S_DATA, S_YTD, S_ORDER_CNT, S_REMOTE_CNT, S_DIST_03 FROM STOCK WHERE S_I_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("UPDATE STOCK SET S_QUANTITY = 3, S_YTD = 3, S_ORDER_CNT = 3, S_REMOTE_CNT = 3 WHERE S_I_ID = 3 AND W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("INSERT INTO ORDER_LINE (OL_O_ID, OL_D_ID, W_ID, OL_NUMBER, OL_I_ID, OL_SUPPLY_W_ID, OL_DELIVERY_D, OL_QUANTITY, OL_AMOUNT, OL_DIST_INFO) VALUES (3, 3, 5, 3, 3, 3, 3, 3, 3, 3)"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT C_ID, C_FIRST, C_MIDDLE, C_LAST, C_BALANCE FROM CUSTOMER WHERE W_ID = 5 AND C_D_ID = 3 AND C_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT C_ID, C_FIRST, C_MIDDLE, C_LAST, C_BALANCE FROM CUSTOMER WHERE W_ID = 5 AND C_D_ID = 3 AND C_LAST = '3' ORDER BY C_FIRST"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT O_ID, O_CARRIER_ID, O_ENTRY_D FROM ORDERS WHERE W_ID = 5 AND O_D_ID = 3 AND O_C_ID = 3 ORDER BY O_ID DESC LIMIT 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT OL_SUPPLY_W_ID, OL_I_ID, OL_QUANTITY, OL_AMOUNT, OL_DELIVERY_D FROM ORDER_LINE WHERE W_ID = 5 AND OL_D_ID = 3 AND OL_O_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT W_NAME, W_STREET_1, W_STREET_2, W_CITY, W_STATE, W_ZIP FROM WAREHOUSE WHERE W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("UPDATE WAREHOUSE SET W_YTD = W_YTD + 3 WHERE W_ID = 5"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT D_NAME, D_STREET_1, D_STREET_2, D_CITY, D_STATE, D_ZIP FROM DISTRICT WHERE W_ID = 5 AND D_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("UPDATE DISTRICT SET D_YTD = D_YTD + 3 WHERE W_ID  = 5 AND D_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT C_ID, C_FIRST, C_MIDDLE, C_LAST, C_STREET_1, C_STREET_2, C_CITY, C_STATE, C_ZIP, C_PHONE, C_SINCE, C_CREDIT, C_CREDIT_LIM, C_DISCOUNT, C_BALANCE, C_YTD_PAYMENT, C_PAYMENT_CNT, C_DATA FROM CUSTOMER WHERE W_ID = 5 AND C_D_ID = 3 AND C_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("SELECT C_ID, C_FIRST, C_MIDDLE, C_LAST, C_STREET_1, C_STREET_2, C_CITY, C_STATE, C_ZIP, C_PHONE, C_SINCE, C_CREDIT, C_CREDIT_LIM, C_DISCOUNT, C_BALANCE, C_YTD_PAYMENT, C_PAYMENT_CNT, C_DATA FROM CUSTOMER WHERE W_ID = 5 AND C_D_ID = 3 AND C_LAST = '3' ORDER BY C_FIRST"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("UPDATE CUSTOMER SET C_BALANCE = 3, C_YTD_PAYMENT = 3, C_PAYMENT_CNT = 3, C_DATA = 3 WHERE W_ID = 5 AND C_D_ID = 3 AND C_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard("UPDATE CUSTOMER SET C_BALANCE = 3, C_YTD_PAYMENT = 3, C_PAYMENT_CNT = 3 WHERE W_ID = 5 AND C_D_ID = 3 AND C_ID = 3"),
+            Some(2)
+        );
+
+        assert_eq!(auto_shard("INSERT INTO HISTORY (H_C_ID, H_C_D_ID, H_C_W_ID, H_D_ID, W_ID, H_DATE, H_AMOUNT, H_DATA) VALUES (3, 3, 5, 3, 5, 3, 3, 3)"), Some(2));
+        assert_eq!(
+            auto_shard("SELECT D_NEXT_O_ID FROM DISTRICT WHERE W_ID = 5 AND D_ID = 3"),
+            Some(2)
+        );
+        assert_eq!(
+            auto_shard(
+                "SELECT COUNT(DISTINCT(OL_I_ID)) FROM ORDER_LINE, STOCK
+                 WHERE ORDER_LINE.W_ID = 5
+                 AND OL_D_ID = 3
+                 AND OL_O_ID < 3
+                 AND OL_O_ID >= 3
+                 AND STOCK.W_ID = 5
+                 AND S_I_ID = OL_I_ID
+                 AND S_QUANTITY < 3"
+            ),
+            Some(2)
+        );
+
+        // This is a distributed query and contains two shards
+        assert_eq!(
+            auto_shard(
+                "SELECT COUNT(DISTINCT(OL_I_ID)) FROM ORDER_LINE, STOCK
+                 WHERE ORDER_LINE.W_ID = 5
+                 AND OL_D_ID = 3
+                 AND OL_O_ID < 3
+                 AND OL_O_ID >= 3
+                 AND STOCK.W_ID = 7
+                 AND S_I_ID = OL_I_ID
+                 AND S_QUANTITY < 3"
+            ),
+            None
+        );
+    }
+
     #[test]
     fn test_prepared_statements() {
         let stmt = "SELECT * FROM data WHERE id = $1";
@@ -1458,12 +1854,13 @@ mod test {
         };
 
         QueryRouter::setup();
-        let mut pool_settings = PoolSettings::default();
-        pool_settings.query_parser_enabled = true;
-        pool_settings.plugins = Some(plugins);
-
+        let pool_settings = PoolSettings {
+            query_parser_enabled: true,
+            plugins: Some(plugins),
+            ..Default::default()
+        };
         let mut qr = QueryRouter::new();
-        qr.update_pool_settings(pool_settings);
+        qr.update_pool_settings(&pool_settings);
 
         let query = simple_query("SELECT * FROM pg_database");
         let ast = qr.parse(&query).unwrap();

src/scram.rs

@@ -79,12 +79,12 @@ impl ScramSha256 {
         let server_message = Message::parse(message)?;
 
         if !server_message.nonce.starts_with(&self.nonce) {
-            return Err(Error::ProtocolSyncError(format!("SCRAM")));
+            return Err(Error::ProtocolSyncError("SCRAM".to_string()));
         }
 
         let salt = match general_purpose::STANDARD.decode(&server_message.salt) {
             Ok(salt) => salt,
-            Err(_) => return Err(Error::ProtocolSyncError(format!("SCRAM"))),
+            Err(_) => return Err(Error::ProtocolSyncError("SCRAM".to_string())),
         };
 
         let salted_password = Self::hi(
@@ -166,9 +166,9 @@ impl ScramSha256 {
     pub fn finish(&mut self, message: &BytesMut) -> Result<(), Error> {
         let final_message = FinalMessage::parse(message)?;
 
-        let verifier = match general_purpose::STANDARD.decode(&final_message.value) {
+        let verifier = match general_purpose::STANDARD.decode(final_message.value) {
             Ok(verifier) => verifier,
-            Err(_) => return Err(Error::ProtocolSyncError(format!("SCRAM"))),
+            Err(_) => return Err(Error::ProtocolSyncError("SCRAM".to_string())),
         };
 
         let mut hmac = match Hmac::<Sha256>::new_from_slice(&self.salted_password) {
@@ -230,14 +230,14 @@ impl Message {
             .collect::<Vec<String>>();
 
         if parts.len() != 3 {
-            return Err(Error::ProtocolSyncError(format!("SCRAM")));
+            return Err(Error::ProtocolSyncError("SCRAM".to_string()));
         }
 
         let nonce = str::replace(&parts[0], "r=", "");
         let salt = str::replace(&parts[1], "s=", "");
         let iterations = match str::replace(&parts[2], "i=", "").parse::<u32>() {
             Ok(iterations) => iterations,
-            Err(_) => return Err(Error::ProtocolSyncError(format!("SCRAM"))),
+            Err(_) => return Err(Error::ProtocolSyncError("SCRAM".to_string())),
         };
 
         Ok(Message {
@@ -257,7 +257,7 @@ impl FinalMessage {
     /// Parse the server final validation message.
     pub fn parse(message: &BytesMut) -> Result<FinalMessage, Error> {
         if !message.starts_with(b"v=") || message.len() < 4 {
-            return Err(Error::ProtocolSyncError(format!("SCRAM")));
+            return Err(Error::ProtocolSyncError("SCRAM".to_string()));
         }
 
         Ok(FinalMessage {

src/server.rs

@@ -3,12 +3,14 @@
 use bytes::{Buf, BufMut, BytesMut};
 use fallible_iterator::FallibleIterator;
 use log::{debug, error, info, trace, warn};
+use lru::LruCache;
 use once_cell::sync::Lazy;
 use parking_lot::{Mutex, RwLock};
 use postgres_protocol::message;
-use std::collections::{BTreeSet, HashMap, HashSet};
+use std::collections::{HashMap, HashSet, VecDeque};
 use std::mem;
 use std::net::IpAddr;
+use std::num::NonZeroUsize;
 use std::sync::Arc;
 use std::time::SystemTime;
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, BufStream};
@@ -16,7 +18,7 @@ use tokio::net::TcpStream;
 use tokio_rustls::rustls::{OwnedTrustAnchor, RootCertStore};
 use tokio_rustls::{client::TlsStream, TlsConnector};
 
-use crate::config::{get_config, get_prepared_statements_cache_size, Address, User};
+use crate::config::{get_config, Address, User};
 use crate::constants::*;
 use crate::dns_cache::{AddrSet, CACHED_RESOLVER};
 use crate::errors::{Error, ServerIdentifier};
@@ -197,12 +199,8 @@ impl ServerParameters {
             key = "DateStyle".to_string();
         };
 
-        if TRACKED_PARAMETERS.contains(&key) {
+        if TRACKED_PARAMETERS.contains(&key) || startup {
             self.parameters.insert(key, value);
-        } else {
-            if startup {
-                self.parameters.insert(key, value);
-            }
         }
     }
 
@@ -326,12 +324,16 @@ pub struct Server {
     log_client_parameter_status_changes: bool,
 
     /// Prepared statements
-    prepared_statements: BTreeSet<String>,
+    prepared_statement_cache: Option<LruCache<String, ()>>,
+
+    /// Prepared statement being currently registered on the server.
+    registering_prepared_statement: VecDeque<String>,
 }
 
 impl Server {
     /// Pretend to be the Postgres client and connect to the server given host, port and credentials.
     /// Perform the authentication and return the server in a ready for query state.
+    #[allow(clippy::too_many_arguments)]
     pub async fn startup(
         address: &Address,
         user: &User,
@@ -341,6 +343,7 @@ impl Server {
         auth_hash: Arc<RwLock<Option<String>>>,
         cleanup_connections: bool,
         log_client_parameter_status_changes: bool,
+        prepared_statement_cache_size: usize,
     ) -> Result<Server, Error> {
         let cached_resolver = CACHED_RESOLVER.load();
         let mut addr_set: Option<AddrSet> = None;
@@ -440,10 +443,7 @@ impl Server {
 
                 // Something else?
                 m => {
-                    return Err(Error::SocketError(format!(
-                        "Unknown message: {}",
-                        m as char
-                    )));
+                    return Err(Error::SocketError(format!("Unknown message: {}", { m })));
                 }
             }
         } else {
@@ -461,26 +461,20 @@ impl Server {
             None => &user.username,
         };
 
-        let password = match user.server_password {
-            Some(ref server_password) => Some(server_password),
-            None => match user.password {
-                Some(ref password) => Some(password),
-                None => None,
-            },
+        let password = match user.server_password.as_ref() {
+            Some(server_password) => Some(server_password),
+            None => user.password.as_ref(),
         };
 
         startup(&mut stream, username, database).await?;
 
         let mut process_id: i32 = 0;
         let mut secret_key: i32 = 0;
-        let server_identifier = ServerIdentifier::new(username, &database);
+        let server_identifier = ServerIdentifier::new(username, database);
 
         // We'll be handling multiple packets, but they will all be structured the same.
         // We'll loop here until this exchange is complete.
-        let mut scram: Option<ScramSha256> = match password {
-            Some(password) => Some(ScramSha256::new(password)),
-            None => None,
-        };
+        let mut scram: Option<ScramSha256> = password.map(|password| ScramSha256::new(password));
 
         let mut server_parameters = ServerParameters::new();
 
@@ -725,7 +719,7 @@ impl Server {
                                 }
                             };
 
-                            let fields = match PgErrorMsg::parse(error) {
+                            let fields = match PgErrorMsg::parse(&error) {
                                 Ok(f) => f,
                                 Err(err) => {
                                     return Err(err);
@@ -830,7 +824,13 @@ impl Server {
                         },
                         cleanup_connections,
                         log_client_parameter_status_changes,
-                        prepared_statements: BTreeSet::new(),
+                        prepared_statement_cache: match prepared_statement_cache_size {
+                            0 => None,
+                            _ => Some(LruCache::new(
+                                NonZeroUsize::new(prepared_statement_cache_size).unwrap(),
+                            )),
+                        },
+                        registering_prepared_statement: VecDeque::new(),
                     };
 
                     return Ok(server);
@@ -882,7 +882,7 @@ impl Server {
         self.mirror_send(messages);
         self.stats().data_sent(messages.len());
 
-        match write_all_flush(&mut self.stream, &messages).await {
+        match write_all_flush(&mut self.stream, messages).await {
             Ok(_) => {
                 // Successfully sent to server
                 self.last_activity = SystemTime::now();
@@ -960,7 +960,6 @@ impl Server {
 
                     // There is no more data available from the server.
                     self.data_available = false;
-
                     break;
                 }
 
@@ -969,6 +968,37 @@ impl Server {
                     if self.in_copy_mode {
                         self.in_copy_mode = false;
                     }
+
+                    // Remove the prepared statement from the cache, it has a syntax error or something else bad happened.
+                    if let Some(prepared_stmt_name) =
+                        self.registering_prepared_statement.pop_front()
+                    {
+                        if let Some(ref mut cache) = self.prepared_statement_cache {
+                            if let Some(_removed) = cache.pop(&prepared_stmt_name) {
+                                debug!(
+                                    "Removed {} from prepared statement cache",
+                                    prepared_stmt_name
+                                );
+                            } else {
+                                // Shouldn't happen.
+                                debug!("Prepared statement {} was not cached", prepared_stmt_name);
+                            }
+                        }
+                    }
+
+                    if self.prepared_statement_cache.is_some() {
+                        let error_message = PgErrorMsg::parse(&message)?;
+                        if error_message.message == "cached plan must not change result type" {
+                            warn!("Server {:?} changed schema, dropping connection to clean up prepared statements", self.address);
+                            // This will still result in an error to the client, but this server connection will drop all cached prepared statements
+                            // so that any new queries will be re-prepared
+                            // TODO: Other ideas to solve errors when there are DDL changes after a statement has been prepared
+                            //  - Recreate entire connection pool to force recreation of all server connections
+                            //  - Clear the ConnectionPool's statement cache so that new statement names are generated
+                            //  - Implement a retry (re-prepare) so the client doesn't see an error
+                            self.cleanup_state.needs_cleanup_prepare = true;
+                        }
+                    }
                 }
 
                 // CommandComplete
@@ -1058,6 +1088,11 @@ impl Server {
                 // Buffer until ReadyForQuery shows up, so don't exit the loop yet.
                 'c' => (),
 
+                // Parse complete successfully
+                '1' => {
+                    self.registering_prepared_statement.pop_front();
+                }
+
                 // Anything else, e.g. errors, notices, etc.
                 // Keep buffering until ReadyForQuery shows up.
                 _ => (),
@@ -1079,117 +1114,103 @@ impl Server {
         Ok(bytes)
     }
 
-    /// Add the prepared statement to being tracked by this server.
-    /// The client is processing data that will create a prepared statement on this server.
-    pub fn will_prepare(&mut self, name: &str) {
-        debug!("Will prepare `{}`", name);
+    // Determines if the server already has a prepared statement with the given name
+    // Increments the prepared statement cache hit counter
+    pub fn has_prepared_statement(&mut self, name: &str) -> bool {
+        let cache = match &mut self.prepared_statement_cache {
+            Some(cache) => cache,
+            None => return false,
+        };
 
-        self.prepared_statements.insert(name.to_string());
-        self.stats.prepared_cache_add();
-    }
-
-    /// Check if we should prepare a statement on the server.
-    pub fn should_prepare(&self, name: &str) -> bool {
-        let should_prepare = !self.prepared_statements.contains(name);
-
-        debug!("Should prepare `{}`: {}", name, should_prepare);
-
-        if should_prepare {
-            self.stats.prepared_cache_miss();
-        } else {
+        let has_it = cache.get(name).is_some();
+        if has_it {
             self.stats.prepared_cache_hit();
+        } else {
+            self.stats.prepared_cache_miss();
         }
 
-        should_prepare
+        has_it
     }
 
-    /// Create a prepared statement on the server.
-    pub async fn prepare(&mut self, parse: &Parse) -> Result<(), Error> {
-        debug!("Preparing `{}`", parse.name);
+    fn add_prepared_statement_to_cache(&mut self, name: &str) -> Option<String> {
+        let cache = match &mut self.prepared_statement_cache {
+            Some(cache) => cache,
+            None => return None,
+        };
 
-        let bytes: BytesMut = parse.try_into()?;
-        self.send(&bytes).await?;
-        self.send(&flush()).await?;
-
-        // Read and discard ParseComplete (B)
-        match read_message(&mut self.stream).await {
-            Ok(_) => (),
-            Err(err) => {
-                self.bad = true;
-                return Err(err);
-            }
-        }
-
-        self.prepared_statements.insert(parse.name.to_string());
         self.stats.prepared_cache_add();
 
-        debug!("Prepared `{}`", parse.name);
-
-        Ok(())
-    }
-
-    /// Maintain adequate cache size on the server.
-    pub async fn maintain_cache(&mut self) -> Result<(), Error> {
-        debug!("Cache maintenance run");
-
-        let max_cache_size = get_prepared_statements_cache_size();
-        let mut names = Vec::new();
-
-        while self.prepared_statements.len() >= max_cache_size {
-            // The prepared statmeents are alphanumerically sorted by the BTree.
-            // FIFO.
-            if let Some(name) = self.prepared_statements.pop_last() {
-                names.push(name);
+        // If we evict something, we need to close it on the server
+        if let Some((evicted_name, _)) = cache.push(name.to_string(), ()) {
+            if evicted_name != name {
+                debug!(
+                    "Evicted prepared statement {} from cache, replaced with {}",
+                    evicted_name, name
+                );
+                return Some(evicted_name);
             }
-        }
+        };
 
-        if !names.is_empty() {
-            self.deallocate(names).await?;
-        }
-
-        Ok(())
+        None
     }
 
-    /// Remove the prepared statement from being tracked by this server.
-    /// The client is processing data that will cause the server to close the prepared statement.
-    pub fn will_close(&mut self, name: &str) {
-        debug!("Will close `{}`", name);
+    fn remove_prepared_statement_from_cache(&mut self, name: &str) {
+        let cache = match &mut self.prepared_statement_cache {
+            Some(cache) => cache,
+            None => return,
+        };
 
-        self.prepared_statements.remove(name);
+        self.stats.prepared_cache_remove();
+        cache.pop(name);
     }
 
-    /// Close a prepared statement on the server.
-    pub async fn deallocate(&mut self, names: Vec<String>) -> Result<(), Error> {
-        for name in &names {
-            debug!("Deallocating prepared statement `{}`", name);
+    pub async fn register_prepared_statement(
+        &mut self,
+        parse: &Parse,
+        should_send_parse_to_server: bool,
+    ) -> Result<(), Error> {
+        if !self.has_prepared_statement(&parse.name) {
+            self.registering_prepared_statement
+                .push_back(parse.name.clone());
 
-            let close = Close::new(name);
-            let bytes: BytesMut = close.try_into()?;
+            let mut bytes = BytesMut::new();
 
-            self.send(&bytes).await?;
-        }
+            if should_send_parse_to_server {
+                let parse_bytes: BytesMut = parse.try_into()?;
+                bytes.extend_from_slice(&parse_bytes);
+            }
 
-        if !names.is_empty() {
-            self.send(&flush()).await?;
-        }
-
-        // Read and discard CloseComplete (3)
-        for name in &names {
-            match read_message(&mut self.stream).await {
-                Ok(_) => {
-                    self.prepared_statements.remove(name);
-                    self.stats.prepared_cache_remove();
-                    debug!("Closed `{}`", name);
-                }
-
-                Err(err) => {
-                    self.bad = true;
-                    return Err(err);
-                }
+            // If we evict something, we need to close it on the server
+            // We do this by adding it to the messages we're sending to the server before the sync
+            if let Some(evicted_name) = self.add_prepared_statement_to_cache(&parse.name) {
+                self.remove_prepared_statement_from_cache(&evicted_name);
+                let close_bytes: BytesMut = Close::new(&evicted_name).try_into()?;
+                bytes.extend_from_slice(&close_bytes);
             };
-        }
 
-        Ok(())
+            // If we have a parse or close we need to send to the server, send them and sync
+            if !bytes.is_empty() {
+                bytes.extend_from_slice(&sync());
+
+                self.send(&bytes).await?;
+
+                loop {
+                    self.recv(None).await?;
+
+                    if !self.is_data_available() {
+                        break;
+                    }
+                }
+            }
+        };
+
+        // If it's not there, something went bad, I'm guessing bad syntax or permissions error
+        // on the server.
+        if !self.has_prepared_statement(&parse.name) {
+            Err(Error::PreparedStatementError)
+        } else {
+            Ok(())
+        }
     }
 
     /// If the server is still inside a transaction.
@@ -1199,6 +1220,7 @@ impl Server {
         self.in_transaction
     }
 
+    /// Currently copying data from client to server or vice-versa.
     pub fn in_copy_mode(&self) -> bool {
         self.in_copy_mode
     }
@@ -1324,6 +1346,10 @@ impl Server {
 
             if self.cleanup_state.needs_cleanup_prepare {
                 reset_string.push_str("DEALLOCATE ALL;");
+                // Since we deallocated all prepared statements, we need to clear the cache
+                if let Some(cache) = &mut self.prepared_statement_cache {
+                    cache.clear();
+                }
             };
 
             self.query(&reset_string).await?;
@@ -1359,16 +1385,14 @@ impl Server {
     }
 
     pub fn mirror_send(&mut self, bytes: &BytesMut) {
-        match self.mirror_manager.as_mut() {
-            Some(manager) => manager.send(bytes),
-            None => (),
+        if let Some(manager) = self.mirror_manager.as_mut() {
+            manager.send(bytes)
         }
     }
 
     pub fn mirror_disconnect(&mut self) {
-        match self.mirror_manager.as_mut() {
-            Some(manager) => manager.disconnect(),
-            None => (),
+        if let Some(manager) = self.mirror_manager.as_mut() {
+            manager.disconnect()
         }
     }
 
@@ -1391,13 +1415,14 @@ impl Server {
             Arc::new(RwLock::new(None)),
             true,
             false,
+            0,
         )
         .await?;
         debug!("Connected!, sending query.");
         server.send(&simple_query(query)).await?;
         let mut message = server.recv(None).await?;
 
-        Ok(parse_query_message(&mut message).await?)
+        parse_query_message(&mut message).await
     }
 }
 

src/sharding.rs

@@ -64,7 +64,7 @@ impl Sharder {
     fn sha1(&self, key: i64) -> usize {
         let mut hasher = Sha1::new();
 
-        hasher.update(&key.to_string().as_bytes());
+        hasher.update(key.to_string().as_bytes());
 
         let result = hasher.finalize();
 
@@ -202,10 +202,10 @@ mod test {
     #[test]
     fn test_sha1_hash() {
         let sharder = Sharder::new(12, ShardingFunction::Sha1);
-        let ids = vec![
+        let ids = [
             0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
         ];
-        let shards = vec![
+        let shards = [
             4, 7, 8, 3, 6, 0, 0, 10, 3, 11, 1, 7, 4, 4, 11, 2, 5, 0, 8, 3,
         ];
 

src/stats/client.rs

@@ -38,8 +38,10 @@ pub struct ClientStats {
     /// Total time spent waiting for a connection from pool, measures in microseconds
     pub total_wait_time: Arc<AtomicU64>,
 
-    /// Maximum time spent waiting for a connection from pool, measures in microseconds
-    pub max_wait_time: Arc<AtomicU64>,
+    /// When this client started waiting.
+    /// Stored as microseconds since connect_time so it can fit in an AtomicU64 instead
+    /// of us using an "AtomicInstant"
+    pub wait_start: Arc<AtomicU64>,
 
     /// Current state of the client
     pub state: Arc<AtomicClientState>,
@@ -63,7 +65,7 @@ impl Default for ClientStats {
             username: String::new(),
             pool_name: String::new(),
             total_wait_time: Arc::new(AtomicU64::new(0)),
-            max_wait_time: Arc::new(AtomicU64::new(0)),
+            wait_start: Arc::new(AtomicU64::new(0)),
             state: Arc::new(AtomicClientState::new(ClientState::Idle)),
             transaction_count: Arc::new(AtomicU64::new(0)),
             query_count: Arc::new(AtomicU64::new(0)),
@@ -111,6 +113,11 @@ impl ClientStats {
 
     /// Reports a client is waiting for a connection
     pub fn waiting(&self) {
+        // safe to truncate, we only lose info if duration is greater than ~585,000 years
+        self.wait_start.store(
+            Instant::now().duration_since(self.connect_time).as_micros() as u64,
+            Ordering::Relaxed,
+        );
         self.state.store(ClientState::Waiting, Ordering::Relaxed);
     }
 
@@ -134,8 +141,6 @@ impl ClientStats {
     pub fn checkout_time(&self, microseconds: u64) {
         self.total_wait_time
             .fetch_add(microseconds, Ordering::Relaxed);
-        self.max_wait_time
-            .fetch_max(microseconds, Ordering::Relaxed);
     }
 
     /// Report a query executed by a client against a server

src/stats/pool.rs

@@ -4,6 +4,7 @@ use super::{ClientState, ServerState};
 use crate::{config::PoolMode, messages::DataType, pool::PoolIdentifier};
 use std::collections::HashMap;
 use std::sync::atomic::*;
+use tokio::time::Instant;
 
 use crate::pool::get_all_pools;
 
@@ -53,6 +54,7 @@ impl PoolStats {
             );
         }
 
+        let now = Instant::now();
         for client in client_map.values() {
             match map.get_mut(&PoolIdentifier {
                 db: client.pool_name(),
@@ -62,10 +64,16 @@ impl PoolStats {
                     match client.state.load(Ordering::Relaxed) {
                         ClientState::Active => pool_stats.cl_active += 1,
                         ClientState::Idle => pool_stats.cl_idle += 1,
-                        ClientState::Waiting => pool_stats.cl_waiting += 1,
+                        ClientState::Waiting => {
+                            pool_stats.cl_waiting += 1;
+                            // wait_start is measured as microseconds since connect_time
+                            // so compute wait_time as (now() - connect_time) - (wait_start - connect_time)
+                            let duration_since_connect = now.duration_since(client.connect_time());
+                            let wait_time = (duration_since_connect.as_micros() as u64)
+                                - client.wait_start.load(Ordering::Relaxed);
+                            pool_stats.maxwait = std::cmp::max(pool_stats.maxwait, wait_time);
+                        }
                     }
-                    let max_wait = client.max_wait_time.load(Ordering::Relaxed);
-                    pool_stats.maxwait = std::cmp::max(pool_stats.maxwait, max_wait);
                 }
                 None => debug!("Client from an obselete pool"),
             }
@@ -86,11 +94,11 @@ impl PoolStats {
             }
         }
 
-        return map;
+        map
     }
 
     pub fn generate_header() -> Vec<(&'static str, DataType)> {
-        return vec![
+        vec![
             ("database", DataType::Text),
             ("user", DataType::Text),
             ("pool_mode", DataType::Text),
@@ -105,11 +113,11 @@ impl PoolStats {
             ("sv_login", DataType::Numeric),
             ("maxwait", DataType::Numeric),
             ("maxwait_us", DataType::Numeric),
-        ];
+        ]
     }
 
     pub fn generate_row(&self) -> Vec<String> {
-        return vec![
+        vec![
             self.identifier.db.clone(),
             self.identifier.user.clone(),
             self.mode.to_string(),
@@ -124,7 +132,7 @@ impl PoolStats {
             self.sv_login.to_string(),
             (self.maxwait / 1_000_000).to_string(),
             (self.maxwait % 1_000_000).to_string(),
-        ];
+        ]
     }
 }
 

src/stats/server.rs

@@ -49,6 +49,7 @@ pub struct ServerStats {
     pub error_count: Arc<AtomicU64>,
     pub prepared_hit_count: Arc<AtomicU64>,
     pub prepared_miss_count: Arc<AtomicU64>,
+    pub prepared_eviction_count: Arc<AtomicU64>,
     pub prepared_cache_size: Arc<AtomicU64>,
 }
 
@@ -68,6 +69,7 @@ impl Default for ServerStats {
             reporter: get_reporter(),
             prepared_hit_count: Arc::new(AtomicU64::new(0)),
             prepared_miss_count: Arc::new(AtomicU64::new(0)),
+            prepared_eviction_count: Arc::new(AtomicU64::new(0)),
             prepared_cache_size: Arc::new(AtomicU64::new(0)),
         }
     }
@@ -221,6 +223,7 @@ impl ServerStats {
     }
 
     pub fn prepared_cache_remove(&self) {
+        self.prepared_eviction_count.fetch_add(1, Ordering::Relaxed);
         self.prepared_cache_size.fetch_sub(1, Ordering::Relaxed);
     }
 }

tests/docker/Dockerfile

@@ -8,3 +8,6 @@ RUN rustup component add llvm-tools-preview
 RUN sudo gem install bundler
 RUN wget -O toxiproxy-2.4.0.deb https://github.com/Shopify/toxiproxy/releases/download/v2.4.0/toxiproxy_2.4.0_linux_$(dpkg --print-architecture).deb && \
 	sudo dpkg -i toxiproxy-2.4.0.deb
+RUN wget -O go1.21.3.linux-$(dpkg --print-architecture).tar.gz https://go.dev/dl/go1.21.3.linux-$(dpkg --print-architecture).tar.gz && \
+    sudo tar -C /usr/local -xzf go1.21.3.linux-$(dpkg --print-architecture).tar.gz && \
+    rm go1.21.3.linux-$(dpkg --print-architecture).tar.gz

tests/go/go.mod

@@ -0,0 +1,5 @@
+module pgcat
+
+go 1.21
+
+require github.com/lib/pq v1.10.9

tests/go/go.sum

@@ -0,0 +1,2 @@
+github.com/lib/pq v1.10.9 h1:YXG7RB+JIjhP29X+OtkiDnYaXQwpS4JEWq7dtCCRUEw=
+github.com/lib/pq v1.10.9/go.mod h1:AlVN5x4E4T544tWzH6hKfbfQvm3HdbOxrmggDNAPY9o=

tests/go/pgcat.toml

@@ -0,0 +1,162 @@
+#
+# PgCat config example.
+#
+
+#
+# General pooler settings
+[general]
+# What IP to run on, 0.0.0.0 means accessible from everywhere.
+host = "0.0.0.0"
+
+# Port to run on, same as PgBouncer used in this example.
+port = "${PORT}"
+
+# Whether to enable prometheus exporter or not.
+enable_prometheus_exporter = true
+
+# Port at which prometheus exporter listens on.
+prometheus_exporter_port = 9930
+
+# How long to wait before aborting a server connection (ms).
+connect_timeout = 1000
+
+# How much time to give the health check query to return with a result (ms).
+healthcheck_timeout = 1000
+
+# How long to keep connection available for immediate re-use, without running a healthcheck query on it
+healthcheck_delay = 30000
+
+# How much time to give clients during shutdown before forcibly killing client connections (ms).
+shutdown_timeout = 5000
+
+# For how long to ban a server if it fails a health check (seconds).
+ban_time = 60 # Seconds
+
+# If we should log client connections
+log_client_connections = false
+
+# If we should log client disconnections
+log_client_disconnections = false
+
+# Reload config automatically if it changes.
+autoreload = 15000
+
+server_round_robin = false
+
+# TLS
+tls_certificate = "../../.circleci/server.cert"
+tls_private_key = "../../.circleci/server.key"
+
+# Credentials to access the virtual administrative database (pgbouncer or pgcat)
+# Connecting to that database allows running commands like `SHOW POOLS`, `SHOW DATABASES`, etc..
+admin_username = "admin_user"
+admin_password = "admin_pass"
+
+# pool
+# configs are structured as pool.<pool_name>
+# the pool_name is what clients use as database name when connecting
+# For the example below a client can connect using "postgres://sharding_user:sharding_user@pgcat_host:pgcat_port/sharded_db"
+[pools.sharded_db]
+# Pool mode (see PgBouncer docs for more).
+# session: one server connection per connected client
+# transaction: one server connection per client transaction
+pool_mode = "transaction"
+
+# If the client doesn't specify, route traffic to
+# this role by default.
+#
+# any: round-robin between primary and replicas,
+# replica: round-robin between replicas only without touching the primary,
+# primary: all queries go to the primary unless otherwise specified.
+default_role = "any"
+
+# Query parser. If enabled, we'll attempt to parse
+# every incoming query to determine if it's a read or a write.
+# If it's a read query, we'll direct it to a replica. Otherwise, if it's a write,
+# we'll direct it to the primary.
+query_parser_enabled = true
+
+# If the query parser is enabled and this setting is enabled, we'll attempt to
+# infer the role from the query itself.
+query_parser_read_write_splitting = true
+
+# If the query parser is enabled and this setting is enabled, the primary will be part of the pool of databases used for
+# load balancing of read queries. Otherwise, the primary will only be used for write
+# queries. The primary can always be explicitely selected with our custom protocol.
+primary_reads_enabled = true
+
+# So what if you wanted to implement a different hashing function,
+# or you've already built one and you want this pooler to use it?
+#
+# Current options:
+#
+# pg_bigint_hash: PARTITION BY HASH (Postgres hashing function)
+# sha1: A hashing function based on SHA1
+#
+sharding_function = "pg_bigint_hash"
+
+# Prepared statements cache size.
+prepared_statements_cache_size = 500
+
+# Credentials for users that may connect to this cluster
+[pools.sharded_db.users.0]
+username = "sharding_user"
+password = "sharding_user"
+# Maximum number of server connections that can be established for this user
+# The maximum number of connection from a single Pgcat process to any database in the cluster
+# is the sum of pool_size across all users.
+pool_size = 5
+statement_timeout = 0
+
+
+[pools.sharded_db.users.1]
+username = "other_user"
+password = "other_user"
+pool_size = 21
+statement_timeout = 30000
+
+# Shard 0
+[pools.sharded_db.shards.0]
+# [ host, port, role ]
+servers = [
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ]
+]
+# Database name (e.g. "postgres")
+database = "shard0"
+
+[pools.sharded_db.shards.1]
+servers = [
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ],
+]
+database = "shard1"
+
+[pools.sharded_db.shards.2]
+servers = [
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ],
+]
+database = "shard2"
+
+
+[pools.simple_db]
+pool_mode = "session"
+default_role = "primary"
+query_parser_enabled = true
+query_parser_read_write_splitting = true
+primary_reads_enabled = true
+sharding_function = "pg_bigint_hash"
+
+[pools.simple_db.users.0]
+username = "simple_user"
+password = "simple_user"
+pool_size = 5
+statement_timeout = 30000
+
+[pools.simple_db.shards.0]
+servers = [
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ]
+]
+database = "some_db"

tests/go/prepared_test.go

@@ -0,0 +1,52 @@
+package pgcat
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	_ "github.com/lib/pq"
+	"testing"
+)
+
+func Test(t *testing.T) {
+	t.Cleanup(setup(t))
+	t.Run("Named parameterized prepared statement works", namedParameterizedPreparedStatement)
+	t.Run("Unnamed parameterized prepared statement works", unnamedParameterizedPreparedStatement)
+}
+
+func namedParameterizedPreparedStatement(t *testing.T) {
+	db, err := sql.Open("postgres", fmt.Sprintf("host=localhost port=%d database=sharded_db user=sharding_user password=sharding_user sslmode=disable", port))
+	if err != nil {
+		t.Fatalf("could not open connection: %+v", err)
+	}
+
+	stmt, err := db.Prepare("SELECT $1")
+
+	if err != nil {
+		t.Fatalf("could not prepare: %+v", err)
+	}
+
+	for i := 0; i < 100; i++ {
+		rows, err := stmt.Query(1)
+		if err != nil {
+			t.Fatalf("could not query: %+v", err)
+		}
+		_ = rows.Close()
+	}
+}
+
+func unnamedParameterizedPreparedStatement(t *testing.T) {
+	db, err := sql.Open("postgres", fmt.Sprintf("host=localhost port=%d database=sharded_db user=sharding_user password=sharding_user sslmode=disable", port))
+	if err != nil {
+		t.Fatalf("could not open connection: %+v", err)
+	}
+
+	for i := 0; i < 100; i++ {
+		// Under the hood QueryContext generates an unnamed parameterized prepared statement
+		rows, err := db.QueryContext(context.Background(), "SELECT $1", 1)
+		if err != nil {
+			t.Fatalf("could not query: %+v", err)
+		}
+		_ = rows.Close()
+	}
+}

tests/go/setup.go

@@ -0,0 +1,81 @@
+package pgcat
+
+import (
+	"context"
+	"database/sql"
+	_ "embed"
+	"fmt"
+	"math/rand"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+//go:embed pgcat.toml
+var pgcatCfg string
+
+var port = rand.Intn(32760-20000) + 20000
+
+func setup(t *testing.T) func() {
+	cfg, err := os.CreateTemp("/tmp", "pgcat_cfg_*.toml")
+	if err != nil {
+		t.Fatalf("could not create temp file: %+v", err)
+	}
+
+	pgcatCfg = strings.Replace(pgcatCfg, "\"${PORT}\"", fmt.Sprintf("%d", port), 1)
+
+	_, err = cfg.Write([]byte(pgcatCfg))
+	if err != nil {
+		t.Fatalf("could not write temp file: %+v", err)
+	}
+
+	commandPath := "../../target/debug/pgcat"
+	if os.Getenv("CARGO_TARGET_DIR") != "" {
+		commandPath = os.Getenv("CARGO_TARGET_DIR") + "/debug/pgcat"
+	}
+
+	cmd := exec.Command(commandPath, cfg.Name())
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	go func() {
+		err = cmd.Run()
+		if err != nil {
+			t.Errorf("could not run pgcat: %+v", err)
+		}
+	}()
+
+	deadline, cancelFunc := context.WithDeadline(context.Background(), time.Now().Add(5*time.Second))
+	defer cancelFunc()
+	for {
+		select {
+		case <-deadline.Done():
+			break
+		case <-time.After(50 * time.Millisecond):
+			db, err := sql.Open("postgres", fmt.Sprintf("host=localhost port=%d database=pgcat user=admin_user password=admin_pass sslmode=disable", port))
+			if err != nil {
+				continue
+			}
+			rows, err := db.QueryContext(deadline, "SHOW STATS")
+			if err != nil {
+				continue
+			}
+			_ = rows.Close()
+			_ = db.Close()
+			break
+		}
+		break
+	}
+
+	return func() {
+		err := cmd.Process.Signal(os.Interrupt)
+		if err != nil {
+			t.Fatalf("could not interrupt pgcat: %+v", err)
+		}
+		err = os.Remove(cfg.Name())
+		if err != nil {
+			t.Fatalf("could not remove temp file: %+v", err)
+		}
+	}
+}

tests/pgbench/simple.sql

@@ -36,4 +36,4 @@ SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
 SET SERVER ROLE TO 'replica';
 
 -- Read load balancing
-SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
+SELECT abalance FROM pgbench_accounts WHERE aid = :aid;

tests/ruby/prepared_spec.rb

@@ -1,29 +1,214 @@
 require_relative 'spec_helper'
 
 describe 'Prepared statements' do
-  let(:processes) { Helpers::Pgcat.three_shard_setup('sharded_db', 5) }
+  let(:pool_size) { 5 }
+  let(:processes) { Helpers::Pgcat.single_instance_setup("sharded_db", pool_size) }
+  let(:prepared_statements_cache_size) { 100 }
+  let(:server_round_robin) { false }
 
-  context 'enabled' do
-    it 'will work over the same connection' do
+  before do
+    new_configs = processes.pgcat.current_config
+    new_configs["general"]["server_round_robin"] = server_round_robin
+    new_configs["pools"]["sharded_db"]["prepared_statements_cache_size"] = prepared_statements_cache_size
+    new_configs["pools"]["sharded_db"]["users"]["0"]["pool_size"] =  pool_size
+    processes.pgcat.update_config(new_configs)
+    processes.pgcat.reload_config
+  end
+
+  context 'when trying prepared statements' do
+    it 'it allows unparameterized statements to succeed' do
+      conn1 = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+      conn2 = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+
+      prepared_query = "SELECT 1"
+      
+      # prepare query on server 1 and client 1
+      conn1.prepare('statement1', prepared_query)
+      conn1.exec_prepared('statement1')
+      
+      conn2.transaction do
+        # Claim server 1 with client 2
+        conn2.exec("SELECT 2")
+      
+        # Client 1 now runs the prepared query, and it's automatically
+        # prepared on server 2
+        conn1.prepare('statement2', prepared_query)
+        conn1.exec_prepared('statement2')
+      
+        # Client 2 now prepares the same query that was already
+        # prepared on server 1. And PgBouncer reuses that already
+        # prepared query for this different client.
+        conn2.prepare('statement3', prepared_query)
+        conn2.exec_prepared('statement3')
+        end
+    ensure
+        conn1.close if conn1
+        conn2.close if conn2
+    end
+
+    it 'it allows parameterized statements to succeed' do
+      conn1 = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+      conn2 = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+
+      prepared_query = "SELECT $1"
+      
+      # prepare query on server 1 and client 1
+      conn1.prepare('statement1', prepared_query)
+      conn1.exec_prepared('statement1', [1])
+    
+      conn2.transaction do
+        # Claim server 1 with client 2
+        conn2.exec("SELECT 2")
+      
+        # Client 1 now runs the prepared query, and it's automatically
+        # prepared on server 2
+        conn1.prepare('statement2', prepared_query)
+        conn1.exec_prepared('statement2', [1])
+      
+        # Client 2 now prepares the same query that was already
+        # prepared on server 1. And PgBouncer reuses that already
+        # prepared query for this different client.
+        conn2.prepare('statement3', prepared_query)
+        conn2.exec_prepared('statement3', [1])
+      end
+    ensure
+       conn1.close if conn1
+       conn2.close if conn2
+
+    end
+  end
+
+  context 'when trying large packets' do
+    it "works with large parse" do
+      conn1 = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+
+      long_string = "1" * 4096 * 10
+      prepared_query = "SELECT '#{long_string}'"
+    
+  
+      # prepare query on server 1 and client 1
+      conn1.prepare('statement1', prepared_query)
+      result = conn1.exec_prepared('statement1')
+    
+      # assert result matches long_string
+      expect(result.getvalue(0, 0)).to eq(long_string)
+    ensure
+      conn1.close if conn1
+    end
+
+    it "works with large bind" do
+      conn1 = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+    
+      long_string = "1" * 4096 * 10
+      prepared_query = "SELECT $1::text"
+    
+      # prepare query on server 1 and client 1
+      conn1.prepare('statement1', prepared_query)
+      result = conn1.exec_prepared('statement1', [long_string])
+    
+      # assert result matches long_string
+      expect(result.getvalue(0, 0)).to eq(long_string)
+    ensure
+      conn1.close if conn1
+    end
+  end
+
+  context 'when statement cache is smaller than set of unqiue statements' do
+    let(:prepared_statements_cache_size) { 1 }
+    let(:pool_size) { 1 }
+
+    it "evicts all but 1 statement from the server cache" do
+      conn = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+
+      5.times do |i|
+        prepared_query = "SELECT '#{i}'"
+        conn.prepare("statement#{i}", prepared_query)
+        result = conn.exec_prepared("statement#{i}")
+        expect(result.getvalue(0, 0)).to eq(i.to_s)
+      end
+
+      # Check number of prepared statements (expected: 1)
+      n_statements = conn.exec("SELECT count(*) FROM pg_prepared_statements").getvalue(0, 0).to_i
+      expect(n_statements).to eq(1)
+    end
+  end
+
+  context 'when statement cache is larger than set of unqiue statements' do
+    let(:pool_size) { 1 }
+
+    it "does not evict any of the statements from the cache" do
+      # cache size 5
+      conn = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+
+      5.times do |i|
+        prepared_query = "SELECT '#{i}'"
+        conn.prepare("statement#{i}", prepared_query)
+        result = conn.exec_prepared("statement#{i}")
+        expect(result.getvalue(0, 0)).to eq(i.to_s)
+      end
+
+      # Check number of prepared statements (expected: 1)
+      n_statements = conn.exec("SELECT count(*) FROM pg_prepared_statements").getvalue(0, 0).to_i
+      expect(n_statements).to eq(5)
+    end
+  end
+
+  context 'when preparing the same query' do
+    let(:prepared_statements_cache_size) { 5 }
+    let(:pool_size) { 5 }
+
+    it "reuses statement cache when there are different statement names on the same connection" do
       conn = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
 
       10.times do |i|
         statement_name = "statement_#{i}"
         conn.prepare(statement_name, 'SELECT $1::int')
         conn.exec_prepared(statement_name, [1])
-        conn.describe_prepared(statement_name)
       end
+
+      # Check number of prepared statements (expected: 1)
+      n_statements = conn.exec("SELECT count(*) FROM pg_prepared_statements").getvalue(0, 0).to_i
+      expect(n_statements).to eq(1)
     end
 
-    it 'will work with new connections' do
-      10.times do
+    it "reuses statement cache when there are different statement names on different connections" do
+      10.times do |i|
         conn = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
-
-        statement_name = 'statement1'
-        conn.prepare('statement1', 'SELECT $1::int')
-        conn.exec_prepared('statement1', [1])
-        conn.describe_prepared('statement1')
+        statement_name = "statement_#{i}"
+        conn.prepare(statement_name, 'SELECT $1::int')
+        conn.exec_prepared(statement_name, [1])
       end
+
+      # Check number of prepared statements (expected: 1)
+      conn = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+      n_statements = conn.exec("SELECT count(*) FROM pg_prepared_statements").getvalue(0, 0).to_i
+      expect(n_statements).to eq(1)
+    end
+  end
+
+  context 'when reloading config' do
+    let(:pool_size) { 1 }
+
+    it "test_reload_config" do
+      conn = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+
+      # prepare query
+      conn.prepare('statement1', 'SELECT 1')
+      conn.exec_prepared('statement1')
+
+      # Reload config which triggers pool recreation
+      new_configs = processes.pgcat.current_config
+      new_configs["pools"]["sharded_db"]["prepared_statements_cache_size"] = prepared_statements_cache_size + 1
+      processes.pgcat.update_config(new_configs)
+      processes.pgcat.reload_config
+
+      # check that we're starting with no prepared statements on the server
+      conn_check = PG.connect(processes.pgcat.connection_string('sharded_db', 'sharding_user'))
+      n_statements = conn_check.exec("SELECT count(*) FROM pg_prepared_statements").getvalue(0, 0).to_i
+      expect(n_statements).to eq(0)
+
+      # still able to run prepared query
+      conn.exec_prepared('statement1')
     end
   end
 end

tests/ruby/stats_spec.rb

@@ -233,7 +233,7 @@ describe "Stats" do
         sleep(1.1) # Allow time for stats to update
         admin_conn = PG::connect(processes.pgcat.admin_connection_string)
         results = admin_conn.async_exec("SHOW POOLS")[0]
-        %w[cl_idle cl_cancel_req sv_idle sv_used sv_tested sv_login maxwait].each do |s|
+        %w[cl_idle cl_cancel_req sv_idle sv_used sv_tested sv_login].each do |s|
           raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
         end
 
@@ -260,12 +260,20 @@ describe "Stats" do
           threads << Thread.new { c.async_exec("SELECT pg_sleep(1.5)") rescue nil }
         end
 
-        sleep(2.5) # Allow time for stats to update
         admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+
+        # two connections waiting => they report wait time
+        sleep(1.1) # Allow time for stats to update
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        expect(results["maxwait"]).to eq("1")
+        expect(results["maxwait_us"].to_i).to be_within(200_000).of(100_000)
+
+        sleep(2.5) # Allow time for stats to update
         results = admin_conn.async_exec("SHOW POOLS")[0]
 
-        expect(results["maxwait"]).to eq("1")
-        expect(results["maxwait_us"].to_i).to be_within(200_000).of(500_000)
+        # no connections waiting => no reported wait time
+        expect(results["maxwait"]).to eq("0")
+        expect(results["maxwait_us"]).to eq("0")
         connections.map(&:close)
 
         sleep(4.5) # Allow time for stats to update
@@ -329,6 +337,40 @@ describe "Stats" do
       admin_conn.close
       connections.map(&:close)
     end
+
+    context "when client has waited for a server" do
+      let(:processes) { Helpers::Pgcat.single_instance_setup("sharded_db", 2) }
+
+      it "shows correct maxwait" do
+        threads = []
+        connections = Array.new(3) { |i| PG::connect("#{pgcat_conn_str}?application_name=app#{i}") }
+        connections.each do |c|
+          threads << Thread.new { c.async_exec("SELECT pg_sleep(1.5)") rescue nil }
+        end
+
+        sleep(2.5) # Allow time for stats to update
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW CLIENTS")
+
+        normal_client_results = results.reject { |r| r["database"] == "pgcat" }
+
+        non_waiting_clients = normal_client_results.select { |c| c["maxwait"] == "0" }
+        waiting_clients = normal_client_results.select { |c| c["maxwait"].to_i > 0 }
+
+        expect(non_waiting_clients.count).to eq(2)
+        non_waiting_clients.each do |client|
+          expect(client["maxwait_us"].to_i).to be_between(0, 50_000)
+        end
+
+        expect(waiting_clients.count).to eq(1)
+        waiting_clients.each do |client|
+          expect(client["maxwait_us"].to_i).to be_within(200_000).of(500_000)
+        end
+
+        admin_conn.close
+        connections.map(&:close)
+      end
+    end
   end
 
 

tests/rust/Cargo.lock

@@ -1206,9 +1206,9 @@ dependencies = [
 
 [[package]]
 name = "webpki"
-version = "0.22.0"
+version = "0.22.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f095d78192e208183081cc07bc5515ef55216397af48b873e5edcd72637fa1bd"
+checksum = "07ecc0cd7cac091bf682ec5efa18b1cff79d617b84181f38b3951dbe135f607f"
 dependencies = [
  "ring",
  "untrusted",

tests/rust/src/main.rs

@@ -16,7 +16,14 @@ async fn test_prepared_statements() {
         let pool = pool.clone();
         let handle = tokio::task::spawn(async move {
             for _ in 0..1000 {
-                sqlx::query("SELECT 1").fetch_all(&pool).await.unwrap();
+                match sqlx::query("SELECT one").fetch_all(&pool).await {
+                    Ok(_) => (),
+                    Err(err) => {
+                        if err.to_string().contains("prepared statement") {
+                            panic!("prepared statement error: {}", err);
+                        }
+                    }
+                }
             }
         });
 

utilities/deb.sh

@@ -22,7 +22,7 @@ mkdir -p "$deb_dir/etc/systemd/system"
 cp target/release/pgcat "$deb_dir/usr/bin/pgcat"
 chmod +x "$deb_dir/usr/bin/pgcat"
 
-cp pgcat.toml "$deb_dir/etc/pgcat.toml"
+cp pgcat.toml "$deb_dir/etc/pgcat.example.toml"
 cp pgcat.service "$deb_dir/etc/systemd/system/pgcat.service"
 
 (cat control | envsubst) > "$deb_dir/DEBIAN/control"