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

Commit1da2a61

Browse files
committed
Back-patch recent fixes for gistchoose and gistRelocateBuildBuffersOnSplit.
This back-ports commitsc8ba697 ande5db11c, which fix one definite and onespeculative bug in gistchoose, and make the code a lot more intelligible aswell. In 9.2 only, this also affects the largely-copied-and-pasted logicin gistRelocateBuildBuffersOnSplit.The impact of the bugs was that the functions might make poor decisionsas to which index tree branch to push a new entry down into, resulting inGiST index bloat and poor performance. The fixes rectify these decisionsfor future insertions, but a REINDEX would be needed to clean up anyexisting index bloat.Alexander Korotkov, Robert Haas, Tom Lane
1 parent4fb505d commit1da2a61

File tree

1 file changed

+73
-25
lines changed

1 file changed

+73
-25
lines changed

‎src/backend/access/gist/gistutil.c‎

Lines changed: 73 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -372,36 +372,55 @@ gistgetadjusted(Relation r, IndexTuple oldtup, IndexTuple addtup, GISTSTATE *gis
372372
}
373373

374374
/*
375-
* find entry with lowest penalty
375+
* Search an upper index page for the entry with lowest penalty for insertion
376+
* of the new index key contained in "it".
377+
*
378+
* Returns the index of the page entry to insert into.
376379
*/
377380
OffsetNumber
378381
gistchoose(Relationr,Pagep,IndexTupleit,/* it has compressed entry */
379382
GISTSTATE*giststate)
380383
{
384+
OffsetNumberresult;
381385
OffsetNumbermaxoff;
382386
OffsetNumberi;
383-
OffsetNumberwhich;
384-
floatsum_grow,
385-
which_grow[INDEX_MAX_KEYS];
387+
floatbest_penalty[INDEX_MAX_KEYS];
386388
GISTENTRYentry,
387389
identry[INDEX_MAX_KEYS];
388390
boolisnull[INDEX_MAX_KEYS];
389391

390-
maxoff=PageGetMaxOffsetNumber(p);
391-
*which_grow=-1.0;
392-
which=InvalidOffsetNumber;
393-
sum_grow=1;
392+
Assert(!GistPageIsLeaf(p));
393+
394394
gistDeCompressAtt(giststate,r,
395395
it,NULL, (OffsetNumber)0,
396396
identry,isnull);
397397

398+
/* we'll return FirstOffsetNumber if page is empty (shouldn't happen) */
399+
result=FirstOffsetNumber;
400+
401+
/*
402+
* The index may have multiple columns, and there's a penalty value for
403+
* each column. The penalty associated with a column that appears earlier
404+
* in the index definition is strictly more important than the penalty of
405+
* a column that appears later in the index definition.
406+
*
407+
* best_penalty[j] is the best penalty we have seen so far for column j,
408+
* or -1 when we haven't yet examined column j. Array entries to the
409+
* right of the first -1 are undefined.
410+
*/
411+
best_penalty[0]=-1;
412+
413+
/*
414+
* Loop over tuples on page.
415+
*/
416+
maxoff=PageGetMaxOffsetNumber(p);
398417
Assert(maxoff >=FirstOffsetNumber);
399-
Assert(!GistPageIsLeaf(p));
400418

401-
for (i=FirstOffsetNumber;i <=maxoff&&sum_grow;i=OffsetNumberNext(i))
419+
for (i=FirstOffsetNumber;i <=maxoff;i=OffsetNumberNext(i))
402420
{
403-
intj;
404421
IndexTupleitup= (IndexTuple)PageGetItem(p,PageGetItemId(p,i));
422+
boolzero_penalty;
423+
intj;
405424

406425
if (!GistPageIsLeaf(p)&&GistTupleIsInvalid(itup))
407426
{
@@ -411,41 +430,70 @@ gistchoose(Relation r, Page p, IndexTuple it,/* it has compressed entry */
411430
continue;
412431
}
413432

414-
sum_grow=0;
433+
zero_penalty= true;
434+
435+
/* Loop over index attributes. */
415436
for (j=0;j<r->rd_att->natts;j++)
416437
{
417438
Datumdatum;
418439
floatusize;
419440
boolIsNull;
420441

442+
/* Compute penalty for this column. */
421443
datum=index_getattr(itup,j+1,giststate->tupdesc,&IsNull);
422444
gistdentryinit(giststate,j,&entry,datum,r,p,i,
423445
FALSE,IsNull);
424446
usize=gistpenalty(giststate,j,&entry,IsNull,
425447
&identry[j],isnull[j]);
448+
if (usize>0)
449+
zero_penalty= false;
426450

427-
if (which_grow[j]<0||usize<which_grow[j])
451+
if (best_penalty[j]<0||usize<best_penalty[j])
452+
{
453+
/*
454+
* New best penalty for column. Tentatively select this tuple
455+
* as the target, and record the best penalty.Then reset the
456+
* next column's penalty to "unknown" (and indirectly, the
457+
* same for all the ones to its right). This will force us to
458+
* adopt this tuple's penalty values as the best for all the
459+
* remaining columns during subsequent loop iterations.
460+
*/
461+
result=i;
462+
best_penalty[j]=usize;
463+
464+
if (j<r->rd_att->natts-1)
465+
best_penalty[j+1]=-1;
466+
}
467+
elseif (best_penalty[j]==usize)
428468
{
429-
which=i;
430-
which_grow[j]=usize;
431-
if (j<r->rd_att->natts-1&&i==FirstOffsetNumber)
432-
which_grow[j+1]=-1;
433-
sum_grow+=which_grow[j];
469+
/*
470+
* The current tuple is exactly as good for this column as the
471+
* best tuple seen so far.The next iteration of this loop
472+
* will compare the next column.
473+
*/
434474
}
435-
elseif (which_grow[j]==usize)
436-
sum_grow+=usize;
437475
else
438476
{
439-
sum_grow=1;
477+
/*
478+
* The current tuple is worse for this column than the best
479+
* tuple seen so far. Skip the remaining columns and move on
480+
* to the next tuple, if any.
481+
*/
482+
zero_penalty= false;/* so outer loop won't exit */
440483
break;
441484
}
442485
}
443-
}
444486

445-
if (which==InvalidOffsetNumber)
446-
which=FirstOffsetNumber;
487+
/*
488+
* If we find a tuple with zero penalty for all columns, there's no
489+
* need to examine remaining tuples; just break out of the loop and
490+
* return it.
491+
*/
492+
if (zero_penalty)
493+
break;
494+
}
447495

448-
returnwhich;
496+
returnresult;
449497
}
450498

451499
/*

0 commit comments

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