Fix native client end() to wait for in-flight pipeline queries

The native client end() was immediately terminating the connection,
causing "Connection terminated" errors for queries still in the pipeline.
Now waits for the drain event before closing when pipelining is active.

Also fix pipeline mode to use sendQueryParams instead of sendQuery,
since PostgreSQL rejects simple query protocol in pipeline mode.

Author: mcollina

packages/pg/lib/native/client.js

@@ -261,16 +261,25 @@ Client.prototype.end = function (cb) {
     })
   }
 
-  this.native.end(function () {
-    self._connected = false
+  const doEnd = function () {
+    self.native.end(function () {
+      self._connected = false
 
-    self._errorAllQueries(new Error('Connection terminated'))
+      self._errorAllQueries(new Error('Connection terminated'))
 
-    process.nextTick(() => {
-      self.emit('end')
-      if (cb) cb()
+      process.nextTick(() => {
+        self.emit('end')
+        if (cb) cb()
+      })
     })
-  })
+  }
+
+  // If pipelining has in-flight or queued queries, wait for them to drain before closing
+  if (this.pipelining && (this._pipeliningInFlight || this._queryQueue.length > 0)) {
+    this.once('drain', doEnd)
+  } else {
+    doEnd()
+  }
   return result
 }