pgpool2.git / summary / log / commit / refs

commit    e84fe9e5a8d93b7b0e347ee2c7d03a26d2dd7296
Author:   Tatsuo Ishii <ishii@sraoss.co.jp>
Date:     Thu Sep 28 22:29:28 2023 +0000

    Fix Describe() so that it does not abort with portal created by DECLARE.
    
    When DECLARE foo CURSOR FOR is executed, a portal named "foo" is
    automatically created by PostgreSQL. As the portal is not managed by
    Pgpool-II, "Describe foo" message failed with "unable to execute
    Describe. unable to get the bind message" error.
    
    To fix this, make Describe() creates a dummy write query context so
    that the describe message is sent to primary (streaming replication
    mode) or all nodes (replication/snapshot isolation mode).
    
    Problem analysis by Heather Lapointe.
    Discussion: https://www.pgpool.net/pipermail/pgpool-general/2023-September/008995.html


 src/protocol/pool_proto_modules.c | 48 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/src/protocol/pool_proto_modules.c b/src/protocol/pool_proto_modules.c
index b1ed1c499..553aebe55 100644
--- a/src/protocol/pool_proto_modules.c
+++ b/src/protocol/pool_proto_modules.c
@@ -112,6 +112,8 @@ static bool multi_statement_query(char *buf);
 
 static void check_prepare(List *parse_tree_list, int len, char *contents);
 
+static POOL_QUERY_CONTEXT *create_dummy_query_context(void);
+
 /*
  * This is the workhorse of processing the pg_terminate_backend function to
  * make sure that the use of function should not trigger the backend node failover.
@@ -1784,14 +1786,22 @@ Describe(POOL_CONNECTION * frontend, POOL_CONNECTION_POOL * backend,
 					(errmsg("Describe message from frontend."),
 					 errdetail("portal: \"%s\"", contents + 1)));
 		msg = pool_get_sent_message('B', contents + 1, POOL_SENT_MESSAGE_CREATED);
-		if (!msg)
-			ereport(FATAL,
-					(return_code(2),
-					 errmsg("unable to execute Describe"),
-					 errdetail("unable to get the bind message")));
 	}
 
-	query_context = msg->query_context;
+	query_context = NULL;
+
+	if (msg)
+		query_context = msg->query_context;
+
+	else if (!msg && *contents == 'P')
+	{
+		/*
+		 * It is possible that client wants to use the portal created by
+		 * DECLARE CUSOR or pl/pgSQL function. If so, the describe message
+		 * should only be sent to primary node.
+		 */
+		query_context = create_dummy_query_context();
+	}
 
 	if (query_context == NULL)
 		ereport(FATAL,
@@ -4888,3 +4898,29 @@ check_prepare(List *parse_tree_list, int len, char *contents)
 		pool_add_sent_message(message);	/* add it to the sent message list */
 	}
 }
+
+/*
+ * Create a dummy query context using get_dummy_insert_query_node().  The
+ * query destination is also set.  As a side effect, query in progress flag is
+ * set.
+ */
+static
+POOL_QUERY_CONTEXT *create_dummy_query_context(void)
+{
+	POOL_QUERY_CONTEXT *query_context;
+	Node	*node;
+	MemoryContext old_context;
+	char	*query = "UNKNOWN QUERY";
+
+	query_context = pool_init_query_context();
+	old_context = MemoryContextSwitchTo(query_context->memory_context);
+
+	node = get_dummy_insert_query_node();
+	pool_start_query(query_context, query, strlen(query), node);
+	pool_where_to_send(query_context, query_context->original_query,
+					   query_context->parse_tree);
+
+	MemoryContextSwitchTo(old_context);
+
+	return query_context;
+}


[parent: bce1eaa6419d]