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, 39 insertions, 8 deletions

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 3fea501b60c..dbaebc88552 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -446,10 +446,6 @@ 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);
@@ -474,6 +470,22 @@ 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)
+			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);
+		}
+
 		attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funcctx->attinmeta = attinmeta;
 
@@ -617,10 +629,6 @@ dblink_record(PG_FUNCTION_ARGS)
 		if (freeconn && PG_NARGS() == 2)
 			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);
@@ -648,6 +656,22 @@ 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)
+			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);
+		}
+
 		attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funcctx->attinmeta = attinmeta;
 
diff --git a/contrib/dblink/doc/cursor b/contrib/dblink/doc/cursor
index 7c9cc3cde25..bf591a4d6e5 100644
--- a/contrib/dblink/doc/cursor
+++ b/contrib/dblink/doc/cursor
@@ -79,6 +79,13 @@ 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');