Add missing optimizer hooks for function cost and number of rows.

Closely follow design of other optimizer hooks: if hook exists
retrieve value from plugin; if still not set then get from cache.

src/backend/utils/cache/lsyscache.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.168 2010/02/26 02:01:11 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.169 2010/04/23 22:23:39 sriggs Exp $
  *
  * NOTES
  *	  Eventually, the index information should go through here, too.
@@ -38,6 +38,9 @@
 /* Hook for plugins to get control in get_attavgwidth() */
 get_attavgwidth_hook_type get_attavgwidth_hook = NULL;
 
+/* Hook for plugins to get control in get_func_cost and get_func_rows */
+get_func_cost_hook_type get_func_cost_hook = NULL;
+get_func_rows_hook_type get_func_rows_hook = NULL;
 
 /*				---------- AMOP CACHES ----------						 */
 
@@ -1409,6 +1412,12 @@ get_func_cost(Oid funcid)
 	HeapTuple	tp;
 	float4		result;
 
+	if (get_func_cost_hook)
+	{
+		result = (*get_func_cost_hook) (funcid);
+		if (result > (float4) 0)
+			return result;
+	}
 	tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
 	if (!HeapTupleIsValid(tp))
 		elog(ERROR, "cache lookup failed for function %u", funcid);
@@ -1428,6 +1437,12 @@ get_func_rows(Oid funcid)
 	HeapTuple	tp;
 	float4		result;
 
+	if (get_func_rows_hook)
+	{
+		result = (*get_func_rows_hook) (funcid);
+		if (result > (float4) 0)
+			return result;
+	}
 	tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
 	if (!HeapTupleIsValid(tp))
 		elog(ERROR, "cache lookup failed for function %u", funcid);

src/include/utils/lsyscache.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/lsyscache.h,v 1.131 2010/01/04 02:44:40 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/lsyscache.h,v 1.132 2010/04/23 22:23:39 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,6 +30,12 @@ typedef enum IOFuncSelector
 typedef int32 (*get_attavgwidth_hook_type) (Oid relid, AttrNumber attnum);
 extern PGDLLIMPORT get_attavgwidth_hook_type get_attavgwidth_hook;
 
+/* Hook for plugins to get control in get_func_cost and get_func_rows */
+typedef float4 (*get_func_cost_hook_type) (Oid funcid);
+extern PGDLLIMPORT get_func_cost_hook_type get_func_cost_hook;
+typedef float4 (*get_func_rows_hook_type) (Oid funcid);
+extern PGDLLIMPORT get_func_rows_hook_type get_func_rows_hook;
+
 extern bool op_in_opfamily(Oid opno, Oid opfamily);
 extern int	get_op_opfamily_strategy(Oid opno, Oid opfamily);
 extern void get_op_opfamily_properties(Oid opno, Oid opfamily,