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Commitfafa374

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Introduce WAL records to log reuse of btree pages, allowing conflict
resolution during Hot Standby. Page reuse interlock requested by Tom.Analysis and patch by me.
1 parent4688869 commitfafa374

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3 files changed

+111
-22
lines changed

3 files changed

+111
-22
lines changed

‎src/backend/access/nbtree/nbtpage.c‎

Lines changed: 56 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.118 2010/02/08 04:33:53 tgl Exp $
12+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.119 2010/02/13 00:59:58 sriggs Exp $
1313
*
1414
*NOTES
1515
* Postgres btree pages look like ordinary relation pages.The opaque
@@ -446,6 +446,48 @@ _bt_checkpage(Relation rel, Buffer buf)
446446
errhint("Please REINDEX it.")));
447447
}
448448

449+
/*
450+
* Log the reuse of a page from the FSM.
451+
*/
452+
staticvoid
453+
_bt_log_reuse_page(Relationrel,BlockNumberblkno,TransactionIdlatestRemovedXid)
454+
{
455+
if (rel->rd_istemp)
456+
return;
457+
458+
/* No ereport(ERROR) until changes are logged */
459+
START_CRIT_SECTION();
460+
461+
/*
462+
* We don't do MarkBufferDirty here because we're about initialise
463+
* the page, and nobody else can see it yet.
464+
*/
465+
466+
/* XLOG stuff */
467+
{
468+
XLogRecPtrrecptr;
469+
XLogRecDatardata[1];
470+
xl_btree_reuse_pagexlrec_reuse;
471+
472+
xlrec_reuse.node=rel->rd_node;
473+
xlrec_reuse.block=blkno;
474+
xlrec_reuse.latestRemovedXid=latestRemovedXid;
475+
rdata[0].data= (char*)&xlrec_reuse;
476+
rdata[0].len=SizeOfBtreeReusePage;
477+
rdata[0].buffer=InvalidBuffer;
478+
rdata[0].next=NULL;
479+
480+
recptr=XLogInsert(RM_BTREE_ID,XLOG_BTREE_REUSE_PAGE,rdata);
481+
482+
/*
483+
* We don't do PageSetLSN or PageSetTLI here because
484+
* we're about initialise the page, so no need.
485+
*/
486+
}
487+
488+
END_CRIT_SECTION();
489+
}
490+
449491
/*
450492
*_bt_getbuf() -- Get a buffer by block number for read or write.
451493
*
@@ -510,7 +552,19 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
510552
{
511553
page=BufferGetPage(buf);
512554
if (_bt_page_recyclable(page))
513-
{
555+
{
556+
/*
557+
* If we are generating WAL for Hot Standby then create
558+
* a WAL record that will allow us to conflict with
559+
* queries running on standby.
560+
*/
561+
if (XLogStandbyInfoActive())
562+
{
563+
BTPageOpaqueopaque= (BTPageOpaque)PageGetSpecialPointer(page);
564+
565+
_bt_log_reuse_page(rel,blkno,opaque->btpo.xact);
566+
}
567+
514568
/* Okay to use page. Re-initialize and return it */
515569
_bt_pageinit(page,BufferGetPageSize(buf));
516570
returnbuf;

‎src/backend/access/nbtree/nbtxlog.c‎

Lines changed: 41 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.60 2010/02/08 04:33:53 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.61 2010/02/13 00:59:58 sriggs Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -814,26 +814,48 @@ btree_redo(XLogRecPtr lsn, XLogRecord *record)
814814
{
815815
uint8info=record->xl_info& ~XLR_INFO_MASK;
816816

817-
/*
818-
* Btree delete records can conflict with standby queries. You might
819-
* think that vacuum records would conflict as well, but we've handled
820-
* that already. XLOG_HEAP2_CLEANUP_INFO records provide the highest xid
821-
* cleaned by the vacuum of the heap and so we can resolve any conflicts
822-
* just once when that arrives. After that any we know that no conflicts
823-
* exist from individual btree vacuum records on that index.
824-
*/
825-
if (InHotStandby&&info==XLOG_BTREE_DELETE)
817+
if (InHotStandby)
826818
{
827-
xl_btree_delete*xlrec= (xl_btree_delete*)XLogRecGetData(record);
819+
switch (info)
820+
{
821+
caseXLOG_BTREE_DELETE:
822+
/*
823+
* Btree delete records can conflict with standby queries. You might
824+
* think that vacuum records would conflict as well, but we've handled
825+
* that already. XLOG_HEAP2_CLEANUP_INFO records provide the highest xid
826+
* cleaned by the vacuum of the heap and so we can resolve any conflicts
827+
* just once when that arrives. After that any we know that no conflicts
828+
* exist from individual btree vacuum records on that index.
829+
*/
830+
{
831+
xl_btree_delete*xlrec= (xl_btree_delete*)XLogRecGetData(record);
828832

829-
/*
830-
* XXX Currently we put everybody on death row, because
831-
* currently _bt_delitems() supplies InvalidTransactionId.
832-
* This can be fairly painful, so providing a better value
833-
* here is worth some thought and possibly some effort to
834-
* improve.
835-
*/
836-
ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid,xlrec->node);
833+
/*
834+
* XXX Currently we put everybody on death row, because
835+
* currently _bt_delitems() supplies InvalidTransactionId.
836+
* This can be fairly painful, so providing a better value
837+
* here is worth some thought and possibly some effort to
838+
* improve.
839+
*/
840+
ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid,xlrec->node);
841+
}
842+
break;
843+
844+
caseXLOG_BTREE_REUSE_PAGE:
845+
/*
846+
* Btree reuse page records exist to provide a conflict point when we
847+
* reuse pages in the index via the FSM. That's all it does though.
848+
*/
849+
{
850+
xl_btree_reuse_page*xlrec= (xl_btree_reuse_page*)XLogRecGetData(record);
851+
852+
ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid,xlrec->node);
853+
}
854+
return;
855+
856+
default:
857+
break;
858+
}
837859
}
838860

839861
/*

‎src/include/access/nbtree.h‎

Lines changed: 14 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.128 2010/02/08 04:33:54 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.129 2010/02/13 00:59:58 sriggs Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -221,6 +221,7 @@ typedef struct BTMetaPageData
221221
#defineXLOG_BTREE_DELETE_PAGE_HALF 0xB0/* page deletion that makes
222222
* parent half-dead */
223223
#defineXLOG_BTREE_VACUUM0xC0/* delete entries on a page during vacuum */
224+
#defineXLOG_BTREE_REUSE_PAGE0xD0/* old page is about to be reused from FSM */
224225

225226
/*
226227
* All that we need to find changed index tuple
@@ -321,6 +322,18 @@ typedef struct xl_btree_delete
321322

322323
#defineSizeOfBtreeDelete(offsetof(xl_btree_delete, latestRemovedXid) + sizeof(TransactionId))
323324

325+
/*
326+
* This is what we need to know about page reuse within btree.
327+
*/
328+
typedefstructxl_btree_reuse_page
329+
{
330+
RelFileNodenode;
331+
BlockNumberblock;
332+
TransactionIdlatestRemovedXid;
333+
}xl_btree_reuse_page;
334+
335+
#defineSizeOfBtreeReusePage(sizeof(xl_btree_reuse_page))
336+
324337
/*
325338
* This is what we need to know about vacuum of individual leaf index tuples.
326339
* The WAL record can represent deletion of any number of index tuples on a

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