Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit94e0333

Browse files
committed
Create a routine PageIndexMultiDelete() that replaces a loop around
PageIndexTupleDelete() with a single pass of compactification ---logic mostly lifted from PageRepairFragmentation. I noticed whileprofiling that a VACUUM that's cleaning up a whole lot of deletedtuples would spend as much as a third of its CPU time inPageIndexTupleDelete; not too surprising considering the loop methodwas roughly O(N^2) in the number of tuples involved.
1 parent775d283 commit94e0333

File tree

4 files changed

+144
-19
lines changed

4 files changed

+144
-19
lines changed

‎src/backend/access/nbtree/nbtpage.c

Lines changed: 3 additions & 8 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 1.81 2004/12/31 21:59:22 pgsql Exp $
12+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.82 2005/03/22 06:17:03 tgl Exp $
1313
*
1414
*NOTES
1515
* Postgres btree pages look like ordinary relation pages.The opaque
@@ -639,17 +639,12 @@ _bt_delitems(Relation rel, Buffer buf,
639639
OffsetNumber*itemnos,intnitems)
640640
{
641641
Pagepage=BufferGetPage(buf);
642-
inti;
643642

644643
/* No ereport(ERROR) until changes are logged */
645644
START_CRIT_SECTION();
646645

647-
/*
648-
* Delete the items in reverse order so we don't have to think about
649-
* adjusting item numbers for previous deletions.
650-
*/
651-
for (i=nitems-1;i >=0;i--)
652-
PageIndexTupleDelete(page,itemnos[i]);
646+
/* Fix the page */
647+
PageIndexMultiDelete(page,itemnos,nitems);
653648

654649
/* XLOG stuff */
655650
if (!rel->rd_istemp)

‎src/backend/access/nbtree/nbtxlog.c

Lines changed: 2 additions & 7 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 1.19 2004/12/31 21:59:22 pgsql Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.20 2005/03/22 06:17:03 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -411,12 +411,7 @@ btree_xlog_delete(bool redo, XLogRecPtr lsn, XLogRecord *record)
411411
unused= (OffsetNumber*) ((char*)xlrec+SizeOfBtreeDelete);
412412
unend= (OffsetNumber*) ((char*)xlrec+record->xl_len);
413413

414-
/* be careful to delete from back to front */
415-
while (unused<unend)
416-
{
417-
unend--;
418-
PageIndexTupleDelete(page,*unend);
419-
}
414+
PageIndexMultiDelete(page,unused,unend-unused);
420415
}
421416

422417
PageSetLSN(page,lsn);

‎src/backend/storage/page/bufpage.c

Lines changed: 137 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.62 2004/12/31 22:01:10 pgsql Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.63 2005/03/22 06:17:03 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -274,13 +274,14 @@ PageRestoreTempPage(Page tempPage, Page oldPage)
274274
}
275275

276276
/*
277-
* sorting support for PageRepairFragmentation
277+
* sorting support for PageRepairFragmentation and PageIndexMultiDelete
278278
*/
279279
typedefstructitemIdSortData
280280
{
281281
intoffsetindex;/* linp array index */
282282
intitemoff;/* page offset of item data */
283283
Sizealignedlen;/* MAXALIGN(item data len) */
284+
ItemIdDataolditemid;/* used only in PageIndexMultiDelete */
284285
}itemIdSortData;
285286
typedefitemIdSortData*itemIdSort;
286287

@@ -297,7 +298,8 @@ itemoffcompare(const void *itemidp1, const void *itemidp2)
297298
*
298299
* Frees fragmented space on a page.
299300
* It doesn't remove unused line pointers! Please don't change this.
300-
* This routine is usable for heap pages only.
301+
*
302+
* This routine is usable for heap pages only, but see PageIndexMultiDelete.
301303
*
302304
* Returns number of unused line pointers on page.If "unused" is not NULL
303305
* then the unused[] array is filled with indexes of unused line pointers.
@@ -543,3 +545,135 @@ PageIndexTupleDelete(Page page, OffsetNumber offnum)
543545
}
544546
}
545547
}
548+
549+
550+
/*
551+
* PageIndexMultiDelete
552+
*
553+
* This routine handles the case of deleting multiple tuples from an
554+
* index page at once. It is considerably faster than a loop around
555+
* PageIndexTupleDelete ... however, the caller *must* supply the array
556+
* of item numbers to be deleted in item number order!
557+
*/
558+
void
559+
PageIndexMultiDelete(Pagepage,OffsetNumber*itemnos,intnitems)
560+
{
561+
PageHeaderphdr= (PageHeader)page;
562+
Offsetpd_lower=phdr->pd_lower;
563+
Offsetpd_upper=phdr->pd_upper;
564+
Offsetpd_special=phdr->pd_special;
565+
itemIdSortitemidbase,
566+
itemidptr;
567+
ItemIdlp;
568+
intnline,
569+
nused;
570+
inti;
571+
Sizetotallen;
572+
Offsetupper;
573+
Sizesize;
574+
unsignedoffset;
575+
intnextitm;
576+
OffsetNumberoffnum;
577+
578+
/*
579+
* If there aren't very many items to delete, then retail
580+
* PageIndexTupleDelete is the best way. Delete the items in reverse
581+
* order so we don't have to think about adjusting item numbers for
582+
* previous deletions.
583+
*
584+
* TODO: tune the magic number here
585+
*/
586+
if (nitems <=2)
587+
{
588+
while (--nitems >=0)
589+
PageIndexTupleDelete(page,itemnos[nitems]);
590+
return;
591+
}
592+
593+
/*
594+
* As with PageRepairFragmentation, paranoia seems justified.
595+
*/
596+
if (pd_lower<SizeOfPageHeaderData||
597+
pd_lower>pd_upper||
598+
pd_upper>pd_special||
599+
pd_special>BLCKSZ||
600+
pd_special!=MAXALIGN(pd_special))
601+
ereport(ERROR,
602+
(errcode(ERRCODE_DATA_CORRUPTED),
603+
errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
604+
pd_lower,pd_upper,pd_special)));
605+
606+
/*
607+
* Scan the item pointer array and build a list of just the ones we
608+
* are going to keep. Notice we do not modify the page yet, since
609+
* we are still validity-checking.
610+
*/
611+
nline=PageGetMaxOffsetNumber(page);
612+
itemidbase= (itemIdSort)palloc(sizeof(itemIdSortData)*nline);
613+
itemidptr=itemidbase;
614+
totallen=0;
615+
nused=0;
616+
nextitm=0;
617+
for (offnum=1;offnum <=nline;offnum++)
618+
{
619+
lp=PageGetItemId(page,offnum);
620+
size=ItemIdGetLength(lp);
621+
offset=ItemIdGetOffset(lp);
622+
if (offset<pd_upper||
623+
(offset+size)>pd_special||
624+
offset!=MAXALIGN(offset))
625+
ereport(ERROR,
626+
(errcode(ERRCODE_DATA_CORRUPTED),
627+
errmsg("corrupted item pointer: offset = %u, size = %u",
628+
offset, (unsignedint)size)));
629+
630+
if (nextitm<nitems&&offnum==itemnos[nextitm])
631+
{
632+
/* skip item to be deleted */
633+
nextitm++;
634+
}
635+
else
636+
{
637+
itemidptr->offsetindex=nused;/* where it will go */
638+
itemidptr->itemoff=offset;
639+
itemidptr->olditemid=*lp;
640+
itemidptr->alignedlen=MAXALIGN(size);
641+
totallen+=itemidptr->alignedlen;
642+
itemidptr++;
643+
nused++;
644+
}
645+
}
646+
647+
/* this will catch invalid or out-of-order itemnos[] */
648+
if (nextitm!=nitems)
649+
elog(ERROR,"incorrect index offsets supplied");
650+
651+
if (totallen> (Size) (pd_special-pd_lower))
652+
ereport(ERROR,
653+
(errcode(ERRCODE_DATA_CORRUPTED),
654+
errmsg("corrupted item lengths: total %u, available space %u",
655+
(unsignedint)totallen,pd_special-pd_lower)));
656+
657+
/* sort itemIdSortData array into decreasing itemoff order */
658+
qsort((char*)itemidbase,nused,sizeof(itemIdSortData),
659+
itemoffcompare);
660+
661+
/* compactify page and install new itemids */
662+
upper=pd_special;
663+
664+
for (i=0,itemidptr=itemidbase;i<nused;i++,itemidptr++)
665+
{
666+
lp=PageGetItemId(page,itemidptr->offsetindex+1);
667+
upper-=itemidptr->alignedlen;
668+
memmove((char*)page+upper,
669+
(char*)page+itemidptr->itemoff,
670+
itemidptr->alignedlen);
671+
*lp=itemidptr->olditemid;
672+
lp->lp_off=upper;
673+
}
674+
675+
phdr->pd_lower=SizeOfPageHeaderData+nused*sizeof(ItemIdData);
676+
phdr->pd_upper=upper;
677+
678+
pfree(itemidbase);
679+
}

‎src/include/storage/bufpage.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.63 2004/12/31 22:03:42 pgsql Exp $
10+
* $PostgreSQL: pgsql/src/include/storage/bufpage.h,v 1.64 2005/03/22 06:17:03 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -323,5 +323,6 @@ extern void PageRestoreTempPage(Page tempPage, Page oldPage);
323323
externintPageRepairFragmentation(Pagepage,OffsetNumber*unused);
324324
externSizePageGetFreeSpace(Pagepage);
325325
externvoidPageIndexTupleDelete(Pagepage,OffsetNumberoffset);
326+
externvoidPageIndexMultiDelete(Pagepage,OffsetNumber*itemnos,intnitems);
326327

327328
#endif/* BUFPAGE_H */

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp