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, 4 insertions, 1 deletions

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 4ee1cc711cd..26a3c5ddc2c 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.232 2007/02/01 19:10:25 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.233 2007/02/07 23:11:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1628,6 +1628,7 @@ CommitTransaction(void)
 	AtEOXact_Namespace(true);
 	/* smgrcommit already done */
 	AtEOXact_Files();
+	pgstat_clear_snapshot();
 	pgstat_count_xact_commit();
 	pgstat_report_txn_timestamp(0);
 
@@ -1844,6 +1845,7 @@ PrepareTransaction(void)
 	AtEOXact_Namespace(true);
 	/* smgrcommit already done */
 	AtEOXact_Files();
+	pgstat_clear_snapshot();
 
 	CurrentResourceOwner = NULL;
 	ResourceOwnerDelete(TopTransactionResourceOwner);
@@ -1995,6 +1997,7 @@ AbortTransaction(void)
 	AtEOXact_Namespace(false);
 	smgrabort();
 	AtEOXact_Files();
+	pgstat_clear_snapshot();
 	pgstat_count_xact_rollback();
 	pgstat_report_txn_timestamp(0);