Fix performance regression in dblink connection speed.

Previous commit e5de601267d98c5d60df6de8d436685c7105d149 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
index cc8714dae62a0ff13dbaa2bde510eed05172f138..a48949334d58a1a43029d26387f3a4b891bbc91b 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -191,7 +191,8 @@ typedef struct remoteConnHashEnt
                                                         errdetail("%s", msg))); \
                                } \
                                dblink_security_check(conn, rconn); \
-                               PQsetClientEncoding(conn, GetDatabaseEncodingName()); \
+                               if (PQclientEncoding(conn) != GetDatabaseEncoding()) \
+                                       PQsetClientEncoding(conn, GetDatabaseEncodingName()); \
                                freeconn = true; \
                        } \
        } while (0)
@@ -270,8 +271,9 @@ 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)
        {