Fix performance regression in dblink connection speed.

jconway · jconway · commit d6ca510d9dba · 2013-12-07T17:00:26.000-08:00
Previous commit e5de601 modified dblink to ensure client encoding matched the server. However the added PQsetClientEncoding() call added significant overhead. Restore original performance in the common case where client encoding already matches server encoding by doing nothing in that case. Applies to all active branches. Issue reported and work sponsored by Zonar Systems.
diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
@@ -209,7 +209,8 @@ typedef struct remoteConnHashEnt
 							 errdetail_internal("%s", msg))); \
 				} \
 				dblink_security_check(conn, rconn); \
-				PQsetClientEncoding(conn, GetDatabaseEncodingName()); \
+				if (PQclientEncoding(conn) != GetDatabaseEncoding()) \
+					PQsetClientEncoding(conn, GetDatabaseEncodingName()); \
 				freeconn = true; \
 			} \
 	} while (0)
@@ -288,8 +289,9 @@ dblink_connect(PG_FUNCTION_ARGS)
 	/* check password actually used if not superuser */
 	dblink_security_check(conn, rconn);
 
-	/* attempt to set client encoding to match server encoding */
-	PQsetClientEncoding(conn, GetDatabaseEncodingName());
+	/* attempt to set client encoding to match server encoding, if needed */
+	if (PQclientEncoding(conn) != GetDatabaseEncoding())
+		PQsetClientEncoding(conn, GetDatabaseEncodingName());
 
 	if (connname)
 	{
