When the remote query result has a different number of columns

than the local query specifies (e.g. in the FROM clause),
throw an ERROR (instead of crashing). Fix for bug #2129 reported
by Akio Iwaasa.

Author: jconway

contrib/dblink/README.dblink

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * Copyright (c) 2001-2005, PostgreSQL Global Development Group
+ * Copyright (c) 2001-2006, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  * 
  * Permission to use, copy, modify, and distribute this software and its

contrib/dblink/dblink.c

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * Copyright (c) 2001-2005, PostgreSQL Global Development Group
+ * Copyright (c) 2001-2006, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  *
  * Permission to use, copy, modify, and distribute this software and its
@@ -579,14 +579,6 @@ dblink_fetch(PG_FUNCTION_ARGS)
 		/* got results, keep track of them */
 		funcctx->user_fctx = res;
 
-		/* fast track when no results */
-		if (funcctx->max_calls < 1)
-		{
-			if (res)
-				PQclear(res);
-			SRF_RETURN_DONE(funcctx);
-		}
-
 		/* get a tuple descriptor for our result type */
 		switch (get_call_result_type(fcinfo, NULL, &tupdesc))
 		{
@@ -609,6 +601,21 @@ dblink_fetch(PG_FUNCTION_ARGS)
 		/* make sure we have a persistent copy of the tupdesc */
 		tupdesc = CreateTupleDescCopy(tupdesc);
 
+		/* check result and tuple descriptor have the same number of columns */
+		if (PQnfields(res) != tupdesc->natts)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+				errmsg("remote query result rowtype does not match "
+						"the specified FROM clause rowtype")));
+
+		/* fast track when no results */
+		if (funcctx->max_calls < 1)
+		{
+			if (res)
+				PQclear(res);
+			SRF_RETURN_DONE(funcctx);
+		}
+
 		/* store needed metadata for subsequent calls */
 		attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funcctx->attinmeta = attinmeta;
@@ -778,14 +785,6 @@ dblink_record(PG_FUNCTION_ARGS)
 		if (freeconn)
 			PQfinish(conn);
 
-		/* fast track when no results */
-		if (funcctx->max_calls < 1)
-		{
-			if (res)
-				PQclear(res);
-			SRF_RETURN_DONE(funcctx);
-		}
-
 		if (!is_sql_cmd)
 		{
 			/* get a tuple descriptor for our result type */
@@ -811,6 +810,21 @@ dblink_record(PG_FUNCTION_ARGS)
 			tupdesc = CreateTupleDescCopy(tupdesc);
 		}
 
+		/* check result and tuple descriptor have the same number of columns */
+		if (PQnfields(res) != tupdesc->natts)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+				errmsg("remote query result rowtype does not match "
+						"the specified FROM clause rowtype")));
+
+		/* fast track when no results */
+		if (funcctx->max_calls < 1)
+		{
+			if (res)
+				PQclear(res);
+			SRF_RETURN_DONE(funcctx);
+		}
+
 		/* store needed metadata for subsequent calls */
 		attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funcctx->attinmeta = attinmeta;

contrib/dblink/dblink.h

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * Copyright (c) 2001-2005, PostgreSQL Global Development Group
+ * Copyright (c) 2001-2006, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  *
  * Permission to use, copy, modify, and distribute this software and its

contrib/dblink/doc/cursor

@@ -92,6 +92,13 @@ Outputs
 
   Returns setof record
 
+Note
+
+  On a mismatch between the number of return fields as specified in the FROM
+  clause, and the actual number of fields returned by the remote cursor, an
+  ERROR will be thrown. In this event, the remote cursor is still advanced
+  by as many rows as it would have been if the ERROR had not occurred.
+
 Example usage
 
 test=# select dblink_connect('dbname=postgres');