Support for prepared statements (#474)

* Start prepared statements

* parse

* Ok

* optional

* dont rewrite anonymous prepared stmts

* Dont rewrite anonymous prep statements

* hm?

* prep statements

* I see!

* comment

* Print config value

* Rewrite bind and add sqlx test

* fmt

* ok

* Fix

* Fix stats

* its late

* clean up PREPARE

src/stats/server.rs

@@ -47,6 +47,8 @@ pub struct ServerStats {
     pub transaction_count: Arc<AtomicU64>,
     pub query_count: Arc<AtomicU64>,
     pub error_count: Arc<AtomicU64>,
+    pub prepared_hit_count: Arc<AtomicU64>,
+    pub prepared_miss_count: Arc<AtomicU64>,
 }
 
 impl Default for ServerStats {
@@ -63,6 +65,8 @@ impl Default for ServerStats {
             query_count: Arc::new(AtomicU64::new(0)),
             error_count: Arc::new(AtomicU64::new(0)),
             reporter: get_reporter(),
+            prepared_hit_count: Arc::new(AtomicU64::new(0)),
+            prepared_miss_count: Arc::new(AtomicU64::new(0)),
         }
     }
 }
@@ -172,6 +176,7 @@ impl ServerStats {
         self.set_application(application_name.to_string());
         self.address.stats.query_count_add();
         self.address.stats.query_time_add(milliseconds);
+        self.query_count.fetch_add(1, Ordering::Relaxed);
     }
 
     /// Report a transaction executed by a client a server
@@ -198,4 +203,14 @@ impl ServerStats {
             .fetch_add(amount_bytes as u64, Ordering::Relaxed);
         self.address.stats.bytes_received_add(amount_bytes as u64);
     }
+
+    /// Report a prepared statement that already exists on the server.
+    pub fn prepared_cache_hit(&self) {
+        self.prepared_hit_count.fetch_add(1, Ordering::Relaxed);
+    }
+
+    /// Report a prepared statement that does not exist on the server yet.
+    pub fn prepared_cache_miss(&self) {
+        self.prepared_miss_count.fetch_add(1, Ordering::Relaxed);
+    }
 }