Restore dblink_current_query() to being a C-language function, so as to not

create an ABI break between 8.3 and 8.4.  It is still just a wrapper around
the built-in current_query() function, but at a different implementation
level.  Per my proposal.

Note: this change doesn't break 8.4beta installations, since their
SQL-language definition of the function still works fine.

contrib/dblink/dblink.c

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.80 2009/06/09 16:35:36 joe Exp $
+ * $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.81 2009/06/09 17:41:02 tgl Exp $
  * Copyright (c) 2001-2009, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  *
@@ -1622,6 +1622,20 @@ dblink_build_sql_update(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text(sql));
 }
 
+/*
+ * dblink_current_query
+ * return the current query string
+ * to allow its use in (among other things)
+ * rewrite rules
+ */
+PG_FUNCTION_INFO_V1(dblink_current_query);
+Datum
+dblink_current_query(PG_FUNCTION_ARGS)
+{
+	/* This is now just an alias for the built-in function current_query() */
+	PG_RETURN_DATUM(current_query(fcinfo));
+}
+
 /*************************************************************
  * internal functions
  */

contrib/dblink/dblink.h

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * $PostgreSQL: pgsql/contrib/dblink/dblink.h,v 1.21 2009/01/01 17:23:32 momjian Exp $
+ * $PostgreSQL: pgsql/contrib/dblink/dblink.h,v 1.22 2009/06/09 17:41:02 tgl Exp $
  * Copyright (c) 2001-2009, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  *
@@ -56,5 +56,6 @@ extern Datum dblink_get_pkey(PG_FUNCTION_ARGS);
 extern Datum dblink_build_sql_insert(PG_FUNCTION_ARGS);
 extern Datum dblink_build_sql_delete(PG_FUNCTION_ARGS);
 extern Datum dblink_build_sql_update(PG_FUNCTION_ARGS);
+extern Datum dblink_current_query(PG_FUNCTION_ARGS);
 
 #endif   /* DBLINK_H */

contrib/dblink/dblink.sql.in

-/* $PostgreSQL: pgsql/contrib/dblink/dblink.sql.in,v 1.17 2008/04/05 02:44:42 momjian Exp $ */
+/* $PostgreSQL: pgsql/contrib/dblink/dblink.sql.in,v 1.18 2009/06/09 17:41:02 tgl Exp $ */
 
 -- Adjust this setting to control where the objects get created.
 SET search_path = public;
@@ -165,8 +165,8 @@ LANGUAGE C STRICT;
 
 CREATE OR REPLACE FUNCTION dblink_current_query ()
 RETURNS text
-AS 'SELECT pg_catalog.current_query()'
-LANGUAGE SQL;
+AS 'MODULE_PATHNAME','dblink_current_query'
+LANGUAGE C;
 
 CREATE OR REPLACE FUNCTION dblink_send_query(text, text)
 RETURNS int4