From: Yoshiyuki Asaba <y-asaba at pgfoundry.org>
Date: Wed, 25 Jul 2007 07:01:05 +0000 (+0000)
Subject: Fix hang up when a SELECT query has error inside transaction block. It
X-Git-Tag: V3_4~16
X-Git-Url: http://git.postgresql.org/gitweb/edit?a=commitdiff_plain;h=71c1640a77d0205ee81ad787f3e1706379859148;p=pgpool1.git

Fix hang up when a SELECT query has error inside transaction block. It
occurs only in simple query protocol. We reproduce the bug with the
following operation.

  BEGIN;
  SELECT * FROM non_exist_table; <-- ERROR
  SELECT 1;
---

diff --git a/pool_process_query.c b/pool_process_query.c
index af4ce1f..428817a 100644
--- a/pool_process_query.c
+++ b/pool_process_query.c
@@ -124,6 +124,7 @@ static int load_balance_enabled(POOL_CONNECTION_POOL *backend, char *sql);
 static void start_load_balance(POOL_CONNECTION_POOL *backend);
 static void end_load_balance(POOL_CONNECTION_POOL *backend);
 static POOL_STATUS do_command(POOL_CONNECTION *backend, char *query, int protoMajor, int no_ready_for_query);
+static POOL_STATUS do_error_command(POOL_CONNECTION *backend, int protoMajor);
 static int need_insert_lock(POOL_CONNECTION_POOL *backend, char *query);
 static POOL_STATUS insert_lock(POOL_CONNECTION_POOL *backend, char *query);
 static char *get_insert_command_table_name(char *query);
@@ -2658,13 +2659,11 @@ POOL_STATUS SimpleForwardToFrontend(char kind, POOL_CONNECTION *frontend, POOL_C
 
 		if (select_in_transaction)
 		{
-			do_command(SECONDARY(backend), "send invalid query from pgpool to abort transaction.",
-					   PROTO_MAJOR_V3, 0);
-			pool_write(SECONDARY(backend), "S", 1);
-			res1 = htonl(4);
-			if (pool_write_and_flush(SECONDARY(backend), &res1, sizeof(res1)) < 0)
+			if (TSTATE(backend) != 'E')
 			{
-				return POOL_END;
+				in_load_balance = 0;
+				REPLICATION = 1;
+				do_error_command(SECONDARY(backend), PROTO_MAJOR_V3);
 			}
 			select_in_transaction = 0;
 		}
@@ -3371,6 +3370,68 @@ static POOL_STATUS do_command(POOL_CONNECTION *backend, char *query, int protoMa
 	return deadlock_detected ? POOL_DEADLOCK : POOL_CONTINUE;
 }
 
+/*
+ * Send syntax error query to abort transaction.
+ * We need to sync transaction status in transaction block.
+ * SELECT query is sended to master only.
+ * If SELECT is error, we must abort transaction on other nodes.
+ */
+static POOL_STATUS do_error_command(POOL_CONNECTION *backend, int protoMajor)
+{
+	int len;
+	int status;
+	char kind;
+	char *string;
+	char *error_query = "send invalid query from pgpool to abort transaction";
+
+	/* send the query to the backend */
+	pool_write(backend, "Q", 1);
+	len = strlen(error_query)+1;
+
+	if (protoMajor == PROTO_MAJOR_V3)
+	{
+		int sendlen = htonl(len + 4);
+		pool_write(backend, &sendlen, sizeof(sendlen));
+	}
+
+	if (pool_write_and_flush(backend, error_query, len) < 0)
+	{
+		return POOL_END;
+	}
+
+	/*
+	 * Expecting CompleteCommand
+	 */
+	status = pool_read(backend, &kind, sizeof(kind));
+	if (status < 0)
+	{
+		pool_error("do_command: error while reading message kind");
+		return POOL_END;
+	}
+
+	/*
+	 * read ErrorResponse message
+	 */
+	if (protoMajor == PROTO_MAJOR_V3)
+	{
+		if (pool_read(backend, &len, sizeof(len)) < 0)
+			return POOL_END;
+		len = ntohl(len) - 4;
+		string = pool_read2(backend, len);
+		if (string == NULL)
+			return POOL_END;
+		pool_debug("command tag: %s", string);
+	}
+	else
+	{
+		string = pool_read_string(backend, &len, 0);
+		if (string == NULL)
+			return POOL_END;
+	}
+
+	return POOL_CONTINUE;
+}
+
 /*
  * judge if we need to lock the table
  * to keep SERIAL consistency among servers