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 a1e7e91f23514c906686b42e1cd9823625755f66..17890ee72da1b9a7cf3f5534e4d20d1ac0d48f80 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -193,7 +193,8 @@ 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)
@@ -272,8 +273,9 @@ 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)
        {