Fix a couple of contrib/dblink bugs.

dblink_exec leaked temporary database connections if any error occurred
after connection setup, for example
	SELECT dblink_exec('...connect string...', 'select 1/0');
Add a PG_TRY block to ensure PQfinish gets done when it is needed.
(dblink_record_internal is on the hairy edge of needing similar treatment,
but seems not to be actively broken at the moment.)

Also, in 9.0 and up, only one of the three functions using tuplestore
return mode was properly checking that the query context would allow
a tuplestore result.

Noted while reviewing dblink patch.  Back-patch to all supported branches.

1 files changed, 18 insertions, 6 deletions

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 21a4bbd1c75..6a829a70d69 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -1142,20 +1142,23 @@ PG_FUNCTION_INFO_V1(dblink_exec);
 Datum
 dblink_exec(PG_FUNCTION_ARGS)
 {
+	text	   *volatile sql_cmd_status = NULL;
+	PGconn	   *volatile conn = NULL;
+	volatile bool freeconn = false;
+
+	DBLINK_INIT;
+
+	PG_TRY();
+	{
 	char	   *msg;
 	PGresult   *res = NULL;
-	text	   *sql_cmd_status = NULL;
 	TupleDesc	tupdesc = NULL;
-	PGconn	   *conn = NULL;
 	char	   *connstr = NULL;
 	char	   *sql = NULL;
 	char	   *conname = NULL;
 	remoteConn *rconn = NULL;
-	bool		freeconn = false;
 	bool		fail = true;	/* default to backward compatible behavior */
 
-	DBLINK_INIT;
-
 	if (PG_NARGS() == 3)
 	{
 		/* must be text,text,bool */
@@ -1234,8 +1237,17 @@ dblink_exec(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
 				 errmsg("statement returning results not allowed")));
 	}
+	}
+	PG_CATCH();
+	{
+		/* if needed, close the connection to the database */
+		if (freeconn)
+			PQfinish(conn);
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
 
-	/* if needed, close the connection to the database and cleanup */
+	/* if needed, close the connection to the database */
 	if (freeconn)
 		PQfinish(conn);