From e8cab5fe49c45e9dc2990e36ecd6a42bf01dc4bc Mon Sep 17 00:00:00 2001
From: Teodor Sigaev <teodor@sigaev.ru>
Date: Mon, 27 Jun 2005 12:45:23 +0000
Subject: Concurrency for GiST - full concurrency for
 insert/update/select/vacuum:         - select and vacuum never locks more
 than one page simultaneously         - select (gettuple) hasn't any lock
 across it's calls         - insert never locks more than two page
 simultaneously:                 - during search of leaf to insert it locks
 only one page                   simultaneously                 - while walk
 upward to the root it locked only parent (may be                   non-direct
 parent) and child. One of them X-lock, another may                   be S- or
 X-lock - 'vacuum full' locks index - improve gistgetmulti - simplify XLOG
 records

Fix bug in index_beginscan_internal: LockRelation may clean
  rd_aminfo structure, so move GET_REL_PROCEDURE after LockRelation
---
 src/backend/access/gist/gistutil.c | 48 ++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 18 deletions(-)

(limited to 'src/backend/access/gist/gistutil.c')

diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 735be85f25..e7c985b459 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *          $PostgreSQL: pgsql/src/backend/access/gist/gistutil.c,v 1.2 2005/06/20 10:29:36 teodor Exp $
+ *          $PostgreSQL: pgsql/src/backend/access/gist/gistutil.c,v 1.3 2005/06/27 12:45:22 teodor Exp $
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
@@ -803,8 +803,12 @@ GISTInitBuffer(Buffer b, uint32 f)
 	page = BufferGetPage(b);
 	PageInit(page, pageSize, sizeof(GISTPageOpaqueData));
 
-	opaque = (GISTPageOpaque) PageGetSpecialPointer(page);
+	opaque = GistPageGetOpaque(page);
 	opaque->flags = f;
+	opaque->nsplited = 0;
+	opaque->level = 0;
+	opaque->rightlink = InvalidBlockNumber;
+	memset( &(opaque->nsn), 0, sizeof(GistNSN) );
 }
 
 void
@@ -856,30 +860,38 @@ gistUserPicksplit(Relation r, GistEntryVector *entryvec, GIST_SPLITVEC *v,
 }
 
 Buffer  
-gistReadBuffer(Relation r, BlockNumber blkno) {
+gistNewBuffer(Relation r) {
 	Buffer buffer = InvalidBuffer;
+	bool needLock;
 
-	if ( blkno != P_NEW ) {
-		buffer = ReadBuffer(r, blkno);
-	} else {
-		Page page;
-
-		while(true) {
-			blkno = GetFreeIndexPage(&r->rd_node);
-			if (blkno == InvalidBlockNumber)
-				break;
+	while(true) {
+		BlockNumber blkno = GetFreeIndexPage(&r->rd_node);
+		if (blkno == InvalidBlockNumber)
+			break;
 
-			buffer = ReadBuffer(r, blkno);
-			page = BufferGetPage(buffer);
+		buffer = ReadBuffer(r, blkno);
+		if ( ConditionalLockBuffer(buffer) ) {
+			Page page = BufferGetPage(buffer);
 			if ( GistPageIsDeleted( page ) ) {
 				GistPageSetNonDeleted( page );
 				return buffer;
-			}
-			ReleaseBuffer( buffer );
+			} else
+				LockBuffer(buffer, GIST_UNLOCK);
 		}
 
-		buffer = ReadBuffer(r, P_NEW); 
+		ReleaseBuffer( buffer );
 	}
-	
+
+	needLock = !RELATION_IS_LOCAL(r);
+
+	if (needLock)
+		LockRelationForExtension(r, ExclusiveLock);
+
+	buffer = ReadBuffer(r, P_NEW);
+	LockBuffer(buffer, GIST_EXCLUSIVE);
+
+	if (needLock)
+		UnlockRelationForExtension(r, ExclusiveLock);
+ 
 	return buffer;
 }
-- 
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