From 61b22d3aab48fc462bf7283964fde9b3071a72fd Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 23 Feb 2003 23:20:52 +0000
Subject: [PATCH] btree page recycling can be done as soon as page's next-xact
 label is older than current Xmin; we don't have to wait till it's older than
 GlobalXmin.

---
 src/backend/access/nbtree/nbtpage.c | 4 ++--
 src/backend/storage/ipc/sinval.c    | 9 ++++++---
 src/backend/utils/time/tqual.c      | 5 +++--
 src/include/utils/tqual.h           | 3 ++-
 4 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c
index a9bd393440..c8fb7628ea 100644
--- a/src/backend/access/nbtree/nbtpage.c
+++ b/src/backend/access/nbtree/nbtpage.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.62 2003/02/23 22:43:08 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.63 2003/02/23 23:20:52 tgl Exp $
  *
  *	NOTES
  *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -544,7 +544,7 @@ _bt_page_recyclable(Page page)
 	 */
 	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 	if (P_ISDELETED(opaque) &&
-		TransactionIdPrecedesOrEquals(opaque->btpo.xact, RecentGlobalXmin))
+		TransactionIdPrecedesOrEquals(opaque->btpo.xact, RecentXmin))
 		return true;
 	return false;
 }
diff --git a/src/backend/storage/ipc/sinval.c b/src/backend/storage/ipc/sinval.c
index 239c3bc8d3..fedb438e97 100644
--- a/src/backend/storage/ipc/sinval.c
+++ b/src/backend/storage/ipc/sinval.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.53 2002/11/21 06:36:08 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.54 2003/02/23 23:20:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -298,9 +298,10 @@ GetOldestXmin(bool allDbs)
  * This ensures that the set of transactions seen as "running" by the
  * current xact will not change after it takes the snapshot.
  *
- * Also, we compute the current global xmin (oldest xmin across all running
+ * We also compute the current global xmin (oldest xmin across all running
  * transactions) and save it in RecentGlobalXmin.  This is the same
- * computation done by GetOldestXmin(TRUE).
+ * computation done by GetOldestXmin(TRUE).  The xmin value is also stored
+ * into RecentXmin.
  *----------
  */
 Snapshot
@@ -419,7 +420,9 @@ GetSnapshotData(bool serializable)
 	if (TransactionIdPrecedes(xmin, globalxmin))
 		globalxmin = xmin;
 
+	/* Update globals for use by VACUUM */
 	RecentGlobalXmin = globalxmin;
+	RecentXmin = xmin;
 
 	snapshot->xmin = xmin;
 	snapshot->xmax = xmax;
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index d6a329fa31..f5f0305e91 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -16,7 +16,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.61 2002/10/08 17:17:19 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.62 2003/02/23 23:20:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,7 +33,8 @@ Snapshot	SnapshotDirty = &SnapshotDirtyData;
 Snapshot	QuerySnapshot = NULL;
 Snapshot	SerializableSnapshot = NULL;
 
-/* This is updated by GetSnapshotData: */
+/* These are updated by GetSnapshotData: */
+TransactionId RecentXmin = InvalidTransactionId;
 TransactionId RecentGlobalXmin = InvalidTransactionId;
 
 bool		ReferentialIntegritySnapshotOverride = false;
diff --git a/src/include/utils/tqual.h b/src/include/utils/tqual.h
index 3e3b741321..bba4eac14c 100644
--- a/src/include/utils/tqual.h
+++ b/src/include/utils/tqual.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: tqual.h,v 1.43 2002/09/04 20:31:46 momjian Exp $
+ * $Id: tqual.h,v 1.44 2003/02/23 23:20:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -41,6 +41,7 @@ extern DLLIMPORT Snapshot SnapshotDirty;
 extern DLLIMPORT Snapshot QuerySnapshot;
 extern DLLIMPORT Snapshot SerializableSnapshot;
 
+extern TransactionId RecentXmin;
 extern TransactionId RecentGlobalXmin;
 
 extern bool ReferentialIntegritySnapshotOverride;