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Commit9917e79

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Minor refactoring in heap_page_prune
Pass 'page', 'blockno' and 'maxoff' to heap_prune_chain() asarguments, so that it doesn't need to fetch them from the buffer. Thissaves a few cycles per chain.Remove the "if (off_loc != NULL)" checks, and require the caller topass a non-NULL 'off_loc'. Pass a pointer to a dummy local variablewhen it's not needed. Those checks are cheap, but it's still better toavoid them in the per-chain loops when we can do so easily.The CPU time saving from these changes are hardly measurable, butfewer instructions is good anyway, so why not. I spotted the potentialfor these while reviewing Melanie Plageman's patch set to combineprune and freeze records.Discussion:https://www.postgresql.org/message-id/CAAKRu_abm2tHhrc0QSQa%3D%3DsHe%3DVA1%3Doz1dJMQYUOKuHmu%2B9Xrg%40mail.gmail.com
1 parentf5a2278 commit9917e79

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-22
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‎src/backend/access/heap/pruneheap.c

Lines changed: 15 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -57,10 +57,8 @@ typedef struct
5757
staticHTSV_Resultheap_prune_satisfies_vacuum(PruneState*prstate,
5858
HeapTupletup,
5959
Bufferbuffer);
60-
staticintheap_prune_chain(Bufferbuffer,
61-
OffsetNumberrootoffnum,
62-
int8*htsv,
63-
PruneState*prstate);
60+
staticintheap_prune_chain(Pagepage,BlockNumberblockno,OffsetNumbermaxoff,
61+
OffsetNumberrootoffnum,int8*htsv,PruneState*prstate);
6462
staticvoidheap_prune_record_prunable(PruneState*prstate,TransactionIdxid);
6563
staticvoidheap_prune_record_redirect(PruneState*prstate,
6664
OffsetNumberoffnum,OffsetNumberrdoffnum);
@@ -145,6 +143,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
145143
*/
146144
if (PageIsFull(page)||PageGetHeapFreeSpace(page)<minfree)
147145
{
146+
OffsetNumberdummy_off_loc;
148147
PruneResultpresult;
149148

150149
/*
@@ -153,7 +152,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
153152
* that during on-access pruning with the current implementation.
154153
*/
155154
heap_page_prune(relation,buffer,vistest, false,
156-
&presult,PRUNE_ON_ACCESS,NULL);
155+
&presult,PRUNE_ON_ACCESS,&dummy_off_loc);
157156

158157
/*
159158
* Report the number of tuples reclaimed to pgstats. This is
@@ -296,8 +295,7 @@ heap_page_prune(Relation relation, Buffer buffer,
296295
* Set the offset number so that we can display it along with any
297296
* error that occurred while processing this tuple.
298297
*/
299-
if (off_loc)
300-
*off_loc=offnum;
298+
*off_loc=offnum;
301299

302300
presult->htsv[offnum]=heap_prune_satisfies_vacuum(&prstate,&tup,
303301
buffer);
@@ -315,22 +313,20 @@ heap_page_prune(Relation relation, Buffer buffer,
315313
continue;
316314

317315
/* see preceding loop */
318-
if (off_loc)
319-
*off_loc=offnum;
316+
*off_loc=offnum;
320317

321318
/* Nothing to do if slot is empty */
322319
itemid=PageGetItemId(page,offnum);
323320
if (!ItemIdIsUsed(itemid))
324321
continue;
325322

326323
/* Process this item or chain of items */
327-
presult->ndeleted+=heap_prune_chain(buffer,offnum,
324+
presult->ndeleted+=heap_prune_chain(page,blockno,maxoff,offnum,
328325
presult->htsv,&prstate);
329326
}
330327

331328
/* Clear the offset information once we have processed the given page. */
332-
if (off_loc)
333-
*off_loc=InvalidOffsetNumber;
329+
*off_loc=InvalidOffsetNumber;
334330

335331
/* Any error while applying the changes is critical */
336332
START_CRIT_SECTION();
@@ -452,30 +448,28 @@ heap_prune_satisfies_vacuum(PruneState *prstate, HeapTuple tup, Buffer buffer)
452448
* Returns the number of tuples (to be) deleted from the page.
453449
*/
454450
staticint
455-
heap_prune_chain(Bufferbuffer,OffsetNumberrootoffnum,
456-
int8*htsv,PruneState*prstate)
451+
heap_prune_chain(Pagepage,BlockNumberblockno,OffsetNumbermaxoff,
452+
OffsetNumberrootoffnum,int8*htsv,PruneState*prstate)
457453
{
458454
intndeleted=0;
459-
Pagedp= (Page)BufferGetPage(buffer);
460455
TransactionIdpriorXmax=InvalidTransactionId;
461456
ItemIdrootlp;
462457
HeapTupleHeaderhtup;
463458
OffsetNumberlatestdead=InvalidOffsetNumber,
464-
maxoff=PageGetMaxOffsetNumber(dp),
465459
offnum;
466460
OffsetNumberchainitems[MaxHeapTuplesPerPage];
467461
intnchain=0,
468462
i;
469463

470-
rootlp=PageGetItemId(dp,rootoffnum);
464+
rootlp=PageGetItemId(page,rootoffnum);
471465

472466
/*
473467
* If it's a heap-only tuple, then it is not the start of a HOT chain.
474468
*/
475469
if (ItemIdIsNormal(rootlp))
476470
{
477471
Assert(htsv[rootoffnum]!=-1);
478-
htup= (HeapTupleHeader)PageGetItem(dp,rootlp);
472+
htup= (HeapTupleHeader)PageGetItem(page,rootlp);
479473

480474
if (HeapTupleHeaderIsHeapOnly(htup))
481475
{
@@ -536,7 +530,7 @@ heap_prune_chain(Buffer buffer, OffsetNumber rootoffnum,
536530
if (prstate->marked[offnum])
537531
break;
538532

539-
lp=PageGetItemId(dp,offnum);
533+
lp=PageGetItemId(page,offnum);
540534

541535
/* Unused item obviously isn't part of the chain */
542536
if (!ItemIdIsUsed(lp))
@@ -575,7 +569,7 @@ heap_prune_chain(Buffer buffer, OffsetNumber rootoffnum,
575569
}
576570

577571
Assert(ItemIdIsNormal(lp));
578-
htup= (HeapTupleHeader)PageGetItem(dp,lp);
572+
htup= (HeapTupleHeader)PageGetItem(page,lp);
579573

580574
/*
581575
* Check the tuple XMIN against prior XMAX, if any
@@ -666,8 +660,7 @@ heap_prune_chain(Buffer buffer, OffsetNumber rootoffnum,
666660
/*
667661
* Advance to next chain member.
668662
*/
669-
Assert(ItemPointerGetBlockNumber(&htup->t_ctid)==
670-
BufferGetBlockNumber(buffer));
663+
Assert(ItemPointerGetBlockNumber(&htup->t_ctid)==blockno);
671664
offnum=ItemPointerGetOffsetNumber(&htup->t_ctid);
672665
priorXmax=HeapTupleHeaderGetUpdateXid(htup);
673666
}

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