Add a function pg_stat_clear_snapshot() that discards any statistics snapshot

already collected in the current transaction; this allows plpgsql functions to
watch for stats updates even though they are confined to a single transaction.
Use this instead of the previous kluge involving pg_stat_file() to wait for
the stats collector to update in the stats regression test.  Internally,
decouple storage of stats snapshots from transaction boundaries; they'll
now stick around until someone calls pgstat_clear_snapshot --- which xact.c
still does at transaction end, to maintain the previous behavior.  This makes
the logic a lot cleaner, at the price of a couple dozen cycles per transaction
exit.

1 files changed, 24 insertions, 12 deletions

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 94631969d0e..d011fff76f8 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.37 2007/01/05 22:19:41 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.38 2007/02/07 23:11:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -39,7 +39,6 @@ extern Datum pg_stat_get_last_autoanalyze_time(PG_FUNCTION_ARGS);
 
 extern Datum pg_stat_get_backend_idset(PG_FUNCTION_ARGS);
 extern Datum pg_backend_pid(PG_FUNCTION_ARGS);
-extern Datum pg_stat_reset(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_pid(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_dbid(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_backend_userid(PG_FUNCTION_ARGS);
@@ -57,6 +56,9 @@ extern Datum pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS);
 
+extern Datum pg_stat_clear_snapshot(PG_FUNCTION_ARGS);
+extern Datum pg_stat_reset(PG_FUNCTION_ARGS);
+
 
 Datum
 pg_stat_get_numscans(PG_FUNCTION_ARGS)
@@ -336,16 +338,6 @@ pg_backend_pid(PG_FUNCTION_ARGS)
 	PG_RETURN_INT32(MyProcPid);
 }
 
-/*
- * Built-in function for resetting the counters
- */
-Datum
-pg_stat_reset(PG_FUNCTION_ARGS)
-{
-	pgstat_reset_counters();
-
-	PG_RETURN_BOOL(true);
-}
 
 Datum
 pg_stat_get_backend_pid(PG_FUNCTION_ARGS)
@@ -678,3 +670,23 @@ pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS)
 
 	PG_RETURN_INT64(result);
 }
+
+
+/* Discard the active statistics snapshot */
+Datum
+pg_stat_clear_snapshot(PG_FUNCTION_ARGS)
+{
+	pgstat_clear_snapshot();
+
+	PG_RETURN_VOID();
+}
+
+
+/* Reset all counters for the current database */
+Datum
+pg_stat_reset(PG_FUNCTION_ARGS)
+{
+	pgstat_reset_counters();
+
+	PG_RETURN_VOID();
+}