From d25ada4d7810304ee04b1f4fd9a14ad9ff0c894f Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 9 Jan 2009 18:50:03 +0000
Subject: [PATCH] Fix libpq so that it reports PGRES_EMPTY_QUERY not
 PGRES_COMMAND_OK when an empty query string is passed to PQexecParams and
 related functions.  Its handling of the NoData response to Describe messages
 was subtly incorrect. Per my report of yesterday.

Although I consider this a bug, it's a behavioral change that might affect
applications, so not back-patched.

In passing fix a second issue in the same code: it didn't react well to an
out-of-memory failure while trying to make the PGresult object.
---
 src/interfaces/libpq/fe-protocol3.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 9cd9c6b203..7dba7c2f81 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-protocol3.c,v 1.37 2009/01/01 17:24:03 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-protocol3.c,v 1.38 2009/01/09 18:50:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -297,19 +297,24 @@ pqParseInput3(PGconn *conn)
 					/*
 					 * NoData indicates that we will not be seeing a
 					 * RowDescription message because the statement or portal
-					 * inquired about doesn't return rows. Set up a COMMAND_OK
-					 * result, instead of TUPLES_OK.
-					 */
-					if (conn->result == NULL)
-						conn->result = PQmakeEmptyPGresult(conn,
-														   PGRES_COMMAND_OK);
-
-					/*
-					 * If we're doing a Describe, we're ready to pass the
-					 * result back to the client.
+					 * inquired about doesn't return rows.
+					 *
+					 * If we're doing a Describe, we have to pass something
+					 * back to the client, so set up a COMMAND_OK result,
+					 * instead of TUPLES_OK.  Otherwise we can just ignore
+					 * this message.
 					 */
 					if (conn->queryclass == PGQUERY_DESCRIBE)
+					{
+						if (conn->result == NULL)
+						{
+							conn->result = PQmakeEmptyPGresult(conn,
+															PGRES_COMMAND_OK);
+							if (!conn->result)
+								return;
+						}
 						conn->asyncStatus = PGASYNC_READY;
+					}
 					break;
 				case 't':		/* Parameter Description */
 					if (getParamDescriptions(conn))
-- 
2.11.0