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Commita97bbe1

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Reduce branches in heapgetpage()'s per-tuple loop
Until now, heapgetpage()'s loop over all tuples performed some conditionalchecks for each tuple, even though condition did not change across the loop.This commit fixes that by moving the loop into an inline function. By callingit with different constant arguments, the compiler can generate an optimizedloop for the different conditions, at the price of two per-page checks.For cases of all-visible tables and an isolation level other thanserializable, speedups of up to 25% have been measured.Reviewed-by: John Naylor <johncnaylorls@gmail.com>Reviewed-by: Zhang Mingli <zmlpostgres@gmail.com>Tested-by: Quan Zongliang <quanzongliang@yeah.net>Discussion:https://postgr.es/m/20230716015656.xjvemfbp5fysjiea@awork3.anarazel.deDiscussion:https://postgr.es/m/2ef7ff1b-3d18-2283-61b1-bbd25fc6c7ce@yeah.net
1 parent41c51f0 commita97bbe1

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1 file changed

+74
-28
lines changed

1 file changed

+74
-28
lines changed

‎src/backend/access/heap/heapam.c

Lines changed: 74 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -364,6 +364,56 @@ heap_setscanlimits(TableScanDesc sscan, BlockNumber startBlk, BlockNumber numBlk
364364
scan->rs_numblocks=numBlks;
365365
}
366366

367+
/*
368+
* Per-tuple loop for heapgetpage() in pagemode. Pulled out so it can be
369+
* called multiple times, with constant arguments for all_visible,
370+
* check_serializable.
371+
*/
372+
pg_attribute_always_inline
373+
staticint
374+
heapgetpage_collect(HeapScanDescscan,Snapshotsnapshot,
375+
Pagepage,Bufferbuffer,
376+
BlockNumberblock,intlines,
377+
boolall_visible,boolcheck_serializable)
378+
{
379+
intntup=0;
380+
OffsetNumberlineoff;
381+
382+
for (lineoff=FirstOffsetNumber;lineoff <=lines;lineoff++)
383+
{
384+
ItemIdlpp=PageGetItemId(page,lineoff);
385+
HeapTupleDataloctup;
386+
boolvalid;
387+
388+
if (!ItemIdIsNormal(lpp))
389+
continue;
390+
391+
loctup.t_data= (HeapTupleHeader)PageGetItem(page,lpp);
392+
loctup.t_len=ItemIdGetLength(lpp);
393+
loctup.t_tableOid=RelationGetRelid(scan->rs_base.rs_rd);
394+
ItemPointerSet(&(loctup.t_self),block,lineoff);
395+
396+
if (all_visible)
397+
valid= true;
398+
else
399+
valid=HeapTupleSatisfiesVisibility(&loctup,snapshot,buffer);
400+
401+
if (check_serializable)
402+
HeapCheckForSerializableConflictOut(valid,scan->rs_base.rs_rd,
403+
&loctup,buffer,snapshot);
404+
405+
if (valid)
406+
{
407+
scan->rs_vistuples[ntup]=lineoff;
408+
ntup++;
409+
}
410+
}
411+
412+
Assert(ntup <=MaxHeapTuplesPerPage);
413+
414+
returnntup;
415+
}
416+
367417
/*
368418
* heap_prepare_pagescan - Prepare current scan page to be scanned in pagemode
369419
*
@@ -379,9 +429,8 @@ heap_prepare_pagescan(TableScanDesc sscan)
379429
Snapshotsnapshot;
380430
Pagepage;
381431
intlines;
382-
intntup;
383-
OffsetNumberlineoff;
384432
boolall_visible;
433+
boolcheck_serializable;
385434

386435
Assert(BufferGetBlockNumber(buffer)==block);
387436

@@ -403,7 +452,6 @@ heap_prepare_pagescan(TableScanDesc sscan)
403452

404453
page=BufferGetPage(buffer);
405454
lines=PageGetMaxOffsetNumber(page);
406-
ntup=0;
407455

408456
/*
409457
* If the all-visible flag indicates that all tuples on the page are
@@ -426,37 +474,35 @@ heap_prepare_pagescan(TableScanDesc sscan)
426474
* tuple for visibility the hard way.
427475
*/
428476
all_visible=PageIsAllVisible(page)&& !snapshot->takenDuringRecovery;
477+
check_serializable=
478+
CheckForSerializableConflictOutNeeded(scan->rs_base.rs_rd,snapshot);
429479

430-
for (lineoff=FirstOffsetNumber;lineoff <=lines;lineoff++)
480+
/*
481+
* We call heapgetpage_collect() with constant arguments, to get the
482+
* compiler to constant fold the constant arguments. Separate calls with
483+
* constant arguments, rather than variables, are needed on several
484+
* compilers to actually perform constant folding.
485+
*/
486+
if (likely(all_visible))
431487
{
432-
ItemIdlpp=PageGetItemId(page,lineoff);
433-
HeapTupleDataloctup;
434-
boolvalid;
435-
436-
if (!ItemIdIsNormal(lpp))
437-
continue;
438-
439-
loctup.t_tableOid=RelationGetRelid(scan->rs_base.rs_rd);
440-
loctup.t_data= (HeapTupleHeader)PageGetItem(page,lpp);
441-
loctup.t_len=ItemIdGetLength(lpp);
442-
ItemPointerSet(&(loctup.t_self),block,lineoff);
443-
444-
if (all_visible)
445-
valid= true;
488+
if (likely(!check_serializable))
489+
scan->rs_ntuples=heapgetpage_collect(scan,snapshot,page,buffer,
490+
block,lines, true, false);
446491
else
447-
valid=HeapTupleSatisfiesVisibility(&loctup,snapshot,buffer);
448-
449-
HeapCheckForSerializableConflictOut(valid,scan->rs_base.rs_rd,
450-
&loctup,buffer,snapshot);
451-
452-
if (valid)
453-
scan->rs_vistuples[ntup++]=lineoff;
492+
scan->rs_ntuples=heapgetpage_collect(scan,snapshot,page,buffer,
493+
block,lines, true, true);
494+
}
495+
else
496+
{
497+
if (likely(!check_serializable))
498+
scan->rs_ntuples=heapgetpage_collect(scan,snapshot,page,buffer,
499+
block,lines, false, false);
500+
else
501+
scan->rs_ntuples=heapgetpage_collect(scan,snapshot,page,buffer,
502+
block,lines, false, true);
454503
}
455504

456505
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
457-
458-
Assert(ntup <=MaxHeapTuplesPerPage);
459-
scan->rs_ntuples=ntup;
460506
}
461507

462508
/*

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