PR #6728 / commit - 1

Add a method to send multiple commands to worker list
reusing the same bare connections. Change will be useful
for metadata sync api.

src/backend/distributed/transaction/worker_transaction.c

@@ -374,6 +374,54 @@ SendCommandListToWorkerOutsideTransactionWithConnection(MultiConnection *workerC
 }
 
 
+/*
+ * SendCommandListToWorkerListWithBareConnections sends the command list
+ * over the specified bare connections. This function is mainly useful to
+ * avoid opening an closing connections excessively by allowing reusing
+ * connections to send multiple separate bare commands. The function
+ * raises an error if any of the queries fail.
+ */
+void
+SendCommandListToWorkerListWithBareConnections(List *workerConnectionList,
+											   List *commandList)
+{
+	Assert(!InCoordinatedTransaction());
+	Assert(!GetCoordinatedTransactionShouldUse2PC());
+
+	if (list_length(commandList) == 0 || list_length(workerConnectionList) == 0)
+	{
+		/* nothing to do */
+		return;
+	}
+
+	/*
+	 * In order to avoid round-trips per query in queryStringList,
+	 * we join the string and send as a single command. Also,
+	 * if there is only a single command, avoid additional call to
+	 * StringJoin given that some strings can be quite large.
+	 */
+	char *stringToSend = (list_length(commandList) == 1) ?
+						 linitial(commandList) : StringJoin(commandList, ';');
+
+	/* send commands in parallel */
+	MultiConnection *connection = NULL;
+	foreach_ptr(connection, workerConnectionList)
+	{
+		int querySent = SendRemoteCommand(connection, stringToSend);
+		if (querySent == 0)
+		{
+			ReportConnectionError(connection, ERROR);
+		}
+	}
+
+	bool failOnError = true;
+	foreach_ptr(connection, workerConnectionList)
+	{
+		ClearResults(connection, failOnError);
+	}
+}
+
+
 /*
  * SendCommandListToWorkerInCoordinatedTransaction opens connection to the node
  * with the given nodeName and nodePort. The commands are sent as part of the

src/include/distributed/worker_transaction.h

@@ -82,6 +82,8 @@ extern void SendCommandListToWorkerOutsideTransaction(const char *nodeName,
 extern void SendCommandListToWorkerOutsideTransactionWithConnection(
 	MultiConnection *workerConnection,
 	List *commandList);
+extern void SendCommandListToWorkerListWithBareConnections(List *workerConnections,
+														   List *commandList);
 extern void SendMetadataCommandListToWorkerListInCoordinatedTransaction(
 	List *workerNodeList,
 	const char *