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.

2 files changed, 35 insertions, 8 deletions

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index a7f2aead50e..4d52f8d1069 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -315,10 +315,6 @@ 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)
-			SRF_RETURN_DONE(funcctx);
-
 		/* check typtype to see if we have a predetermined return type */
 		functypeid = get_func_rettype(funcid);
 		functyptype = get_typtype(functypeid);
@@ -342,6 +338,20 @@ dblink_fetch(PG_FUNCTION_ARGS)
 		/* store needed metadata for subsequent calls */
 		slot = TupleDescGetSlot(tupdesc);
 		funcctx->slot = slot;
+
+		/* check result and tuple descriptor have the same number of columns */
+		if (PQnfields(res) != tupdesc->natts)
+			elog(ERROR, "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);
+		}
+
 		attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funcctx->attinmeta = attinmeta;
 
@@ -500,10 +510,6 @@ dblink_record(PG_FUNCTION_ARGS)
 				PQfinish(conn);
 		}
 
-		/* fast track when no results */
-		if (funcctx->max_calls < 1)
-			SRF_RETURN_DONE(funcctx);
-
 		/* check typtype to see if we have a predetermined return type */
 		functypeid = get_func_rettype(funcid);
 		functyptype = get_typtype(functypeid);
@@ -530,6 +536,20 @@ dblink_record(PG_FUNCTION_ARGS)
 		/* store needed metadata for subsequent calls */
 		slot = TupleDescGetSlot(tupdesc);
 		funcctx->slot = slot;
+
+		/* check result and tuple descriptor have the same number of columns */
+		if (PQnfields(res) != tupdesc->natts)
+			elog(ERROR, "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);
+		}
+
 		attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funcctx->attinmeta = attinmeta;
 
diff --git a/contrib/dblink/doc/cursor b/contrib/dblink/doc/cursor
index 3bc6bdb2fe5..0b9235b4279 100644
--- a/contrib/dblink/doc/cursor
+++ b/contrib/dblink/doc/cursor
@@ -69,6 +69,13 @@ 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=template1');