From 17ffe2ed518b2d892807649b44f2f89f3ee4d4ad Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Mon, 5 Oct 2009 14:28:34 +0100
Subject: [PATCH] Apply
 0007-Need-to-pin-and-take-cleanup-lock-on-every-b-tree-le.patch with some
 docs changes. All code changes approved, especially the neat tweak to improve
 performance in btree vacuum.

---
 src/backend/access/nbtree/nbtxlog.c | 20 +++++++++++++-------
 src/backend/access/transam/clog.c   |  1 -
 src/backend/access/transam/xlog.c   |  6 +++---
 src/include/access/xlog.h           |  1 -
 4 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index aea48d9d54..6b78781b94 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -470,9 +470,6 @@ btree_xlog_vacuum(XLogRecPtr lsn, XLogRecord *record)
 	Page		page;
 	BTPageOpaque opaque;
 
-	if (record->xl_info & XLR_BKP_BLOCK_1)
-		return;
-
 	xlrec = (xl_btree_vacuum *) XLogRecGetData(record);
 
 	/*
@@ -502,6 +499,15 @@ btree_xlog_vacuum(XLogRecPtr lsn, XLogRecord *record)
 		}
 	}
 
+	/*
+	 * If the block was restored from a full page image, nothing more to do.
+	 * The RestoreBkpBlocks() call already pinned and took cleanup lock on
+	 * it. We call RestoreBkpBlocks() after skipping blocks so that we get
+	 * sequential disk access.
+	 */
+	if (record->xl_info & XLR_BKP_BLOCK_1)
+		return;
+
 	/*
 	 * Like in btvacuumpage(), we need to take a cleanup lock on every leaf
 	 * page. See nbtree/README for details.
@@ -830,17 +836,17 @@ btree_redo(XLogRecPtr lsn, XLogRecord *record)
 									true);
 
 			ResolveRecoveryConflictWithVirtualXIDs(backends,
-									"drop tablespace",
+									"b-tree delete",
 									CONFLICT_MODE_ERROR_DEFERRABLE,
 									lsn);
 		}
 	}
 
 	/*
-	 * Exclusive lock on a btree block is as good as a Cleanup lock,
-	 * so need to special case btree delete and vacuum.
+	 * Vacuum needs to pin and take cleanup lock on every leaf page,
+	 * a regular exclusive lock is enough for all other purposes.
 	 */
-	RestoreBkpBlocks(lsn, record, false);
+	RestoreBkpBlocks(lsn, record, (info == XLOG_BTREE_VACUUM));
 
 	switch (info)
 	{
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 90de8b61b5..c6c27a79bc 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -35,7 +35,6 @@
 #include "access/clog.h"
 #include "access/slru.h"
 #include "access/transam.h"
-#include "access/xact.h"
 #include "access/xlogutils.h"
 #include "pg_trace.h"
 #include "postmaster/bgwriter.h"
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8308e22ed0..b5a7f66701 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -3338,9 +3338,9 @@ CleanupBackupHistory(void)
  * ignoring them as already applied, but that's not a huge drawback.
  *
  * If 'cleanup' is true, a cleanup lock is used when restoring blocks.
- * Otherwise, a normal exclusive lock is used.	At the moment, that's just
- * pro forma, because there can't be any regular backends in the system
- * during recovery.  The 'cleanup' argument applies to all backup blocks
+ * Otherwise, a normal exclusive lock is used.	This is important to
+ * safeguard these changes against users accessing the system during recovery.
+ *  The 'cleanup' argument applies to all backup blocks
  * in the WAL record, that suffices for now.
  */
 void
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 7a9308204c..7eec091e61 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -20,7 +20,6 @@
 
 /* Handy constant for an invalid xlog recptr */
 static const XLogRecPtr InvalidXLogRecPtr = {0, 0};
-#define XLogRecPtrIsValid(xp)	(!(xp.xlogid ==0 && xp.xrecoff == 0))
 
 /*
  * The overall layout of an XLOG record is:
-- 
2.39.5