Send DISCARD ALL even if client is not in transaction (#152)

* Send DISCARD ALL even if client is not in transaction

* fmt

* Added tests + avoided sending extra discard all

* Adds set name logic to beginning of handle client

* fmt

* refactor dead code handling

* Refactor reading command tag

* remove unnecessary trim

* Removing debugging statement

* typo

* typo{

* documentation

* edit text

* un-unwrap

* run ci

* run ci

Co-authored-by: Zain Kabani <zain.kabani@instacart.com>

tests/ruby/helpers/pgcat_helper.rb

@@ -5,7 +5,7 @@ require_relative 'pg_instance'
 
 module Helpers
   module Pgcat
-    def self.three_shard_setup(pool_name, pool_size)
+    def self.three_shard_setup(pool_name, pool_size, pool_mode="transaction")
       user = {
         "password" => "sharding_user",
         "pool_size" => pool_size,
@@ -22,7 +22,7 @@ module Helpers
       pgcat_cfg["pools"] = {
         "#{pool_name}" => {
           "default_role" => "any",
-          "pool_mode" => "transaction",
+          "pool_mode" => pool_mode,
           "primary_reads_enabled" => false,
           "query_parser_enabled" => false,
           "sharding_function" => "pg_bigint_hash",
@@ -46,7 +46,7 @@ module Helpers
       end
     end
 
-    def self.single_shard_setup(pool_name, pool_size)
+    def self.single_shard_setup(pool_name, pool_size, pool_mode="transaction")
       user = {
         "password" => "sharding_user",
         "pool_size" => pool_size,
@@ -66,7 +66,7 @@ module Helpers
       pgcat_cfg["pools"] = {
         "#{pool_name}" => {
           "default_role" => "any",
-          "pool_mode" => "transaction",
+          "pool_mode" => pool_mode,
           "primary_reads_enabled" => false,
           "query_parser_enabled" => false,
           "sharding_function" => "pg_bigint_hash",

tests/ruby/misc_spec.rb

@@ -91,7 +91,6 @@ describe "Miscellaneous" do
       conn.close
 
       expect(processes.primary.count_query("ROLLBACK")).to eq(1)
-      expect(processes.primary.count_query("DISCARD ALL")).to eq(1)
     end
   end
 
@@ -106,4 +105,82 @@ describe "Miscellaneous" do
       admin_conn.close
     end
   end
+
+  describe "State clearance" do
+    context "session mode" do
+      let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5, "session") }
+
+      it "Clears state before connection checkin" do
+        # Both modes of operation should not raise
+        # ERROR:  prepared statement "prepared_q" already exists
+        15.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("PREPARE prepared_q (int) AS SELECT $1")
+          conn.close
+        end
+
+        conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+        initial_value = conn.async_exec("SHOW statement_timeout")[0]["statement_timeout"]
+        conn.async_exec("SET statement_timeout to 1000")
+        current_value = conn.async_exec("SHOW statement_timeout")[0]["statement_timeout"]
+        expect(conn.async_exec("SHOW statement_timeout")[0]["statement_timeout"]).to eq("1s")
+        conn.close
+      end
+
+      it "Does not send DISCARD ALL unless necessary" do
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(0)
+
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.async_exec("SET statement_timeout to 5000")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(10)
+      end
+    end
+
+    context "transaction mode" do
+      let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5, "transaction") }
+      it "Clears state before connection checkin" do
+        # Both modes of operation should not raise
+        # ERROR:  prepared statement "prepared_q" already exists
+        15.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("PREPARE prepared_q (int) AS SELECT $1")
+          conn.close
+        end
+      end
+
+      it "Does not send DISCARD ALL unless necessary" do
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(0)
+
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.async_exec("SET statement_timeout to 5000")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(10)
+      end
+    end
+  end
 end