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Commit9e0fe09

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Refactor bitmap heap scan in preparation for parallel support.
The final patch will be less messy if the prefetching support isa bit better isolated, so do that.Dilip Kumar, with some changes by me. The larger patch set of whichthis is a part has been reviewed and tested by (at least) AndresFreund, Amit Khandekar, Tushar Ahuja, Rafia Sabih, Haribabu Kommi, andThomas Munro.
1 parent3c3bb99 commit9e0fe09

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1 file changed

+88
-60
lines changed

1 file changed

+88
-60
lines changed

‎src/backend/executor/nodeBitmapHeapscan.c

Lines changed: 88 additions & 60 deletions
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,11 @@
5353

5454
staticTupleTableSlot*BitmapHeapNext(BitmapHeapScanState*node);
5555
staticvoidbitgetpage(HeapScanDescscan,TBMIterateResult*tbmres);
56+
staticinlinevoidBitmapAdjustPrefetchIterator(BitmapHeapScanState*node,
57+
TBMIterateResult*tbmres);
58+
staticinlinevoidBitmapAdjustPrefetchTarget(BitmapHeapScanState*node);
59+
staticinlinevoidBitmapPrefetch(BitmapHeapScanState*node,
60+
HeapScanDescscan);
5661

5762

5863
/* ----------------------------------------------------------------
@@ -69,10 +74,6 @@ BitmapHeapNext(BitmapHeapScanState *node)
6974
TIDBitmap*tbm;
7075
TBMIterator*tbmiterator;
7176
TBMIterateResult*tbmres;
72-
73-
#ifdefUSE_PREFETCH
74-
TBMIterator*prefetch_iterator;
75-
#endif
7677
OffsetNumbertargoffset;
7778
TupleTableSlot*slot;
7879

@@ -85,9 +86,6 @@ BitmapHeapNext(BitmapHeapScanState *node)
8586
tbm=node->tbm;
8687
tbmiterator=node->tbmiterator;
8788
tbmres=node->tbmres;
88-
#ifdefUSE_PREFETCH
89-
prefetch_iterator=node->prefetch_iterator;
90-
#endif
9189

9290
/*
9391
* If we haven't yet performed the underlying index scan, do it, and begin
@@ -115,7 +113,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
115113
#ifdefUSE_PREFETCH
116114
if (node->prefetch_maximum>0)
117115
{
118-
node->prefetch_iterator=prefetch_iterator=tbm_begin_iterate(tbm);
116+
node->prefetch_iterator=tbm_begin_iterate(tbm);
119117
node->prefetch_pages=0;
120118
node->prefetch_target=-1;
121119
}
@@ -139,21 +137,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
139137
break;
140138
}
141139

142-
#ifdefUSE_PREFETCH
143-
if (node->prefetch_pages>0)
144-
{
145-
/* The main iterator has closed the distance by one page */
146-
node->prefetch_pages--;
147-
}
148-
elseif (prefetch_iterator)
149-
{
150-
/* Do not let the prefetch iterator get behind the main one */
151-
TBMIterateResult*tbmpre=tbm_iterate(prefetch_iterator);
152-
153-
if (tbmpre==NULL||tbmpre->blockno!=tbmres->blockno)
154-
elog(ERROR,"prefetch and main iterators are out of sync");
155-
}
156-
#endif/* USE_PREFETCH */
140+
BitmapAdjustPrefetchIterator(node,tbmres);
157141

158142
/*
159143
* Ignore any claimed entries past what we think is the end of the
@@ -182,23 +166,8 @@ BitmapHeapNext(BitmapHeapScanState *node)
182166
*/
183167
scan->rs_cindex=0;
184168

185-
#ifdefUSE_PREFETCH
186-
187-
/*
188-
* Increase prefetch target if it's not yet at the max. Note that
189-
* we will increase it to zero after fetching the very first
190-
* page/tuple, then to one after the second tuple is fetched, then
191-
* it doubles as later pages are fetched.
192-
*/
193-
if (node->prefetch_target >=node->prefetch_maximum)
194-
/* don't increase any further */ ;
195-
elseif (node->prefetch_target >=node->prefetch_maximum /2)
196-
node->prefetch_target=node->prefetch_maximum;
197-
elseif (node->prefetch_target>0)
198-
node->prefetch_target *=2;
199-
else
200-
node->prefetch_target++;
201-
#endif/* USE_PREFETCH */
169+
/* Adjust the prefetch target */
170+
BitmapAdjustPrefetchTarget(node);
202171
}
203172
else
204173
{
@@ -227,33 +196,14 @@ BitmapHeapNext(BitmapHeapScanState *node)
227196
continue;
228197
}
229198

230-
#ifdefUSE_PREFETCH
231-
232199
/*
233200
* We issue prefetch requests *after* fetching the current page to try
234201
* to avoid having prefetching interfere with the main I/O. Also, this
235202
* should happen only when we have determined there is still something
236203
* to do on the current page, else we may uselessly prefetch the same
237204
* page we are just about to request for real.
238205
*/
239-
if (prefetch_iterator)
240-
{
241-
while (node->prefetch_pages<node->prefetch_target)
242-
{
243-
TBMIterateResult*tbmpre=tbm_iterate(prefetch_iterator);
244-
245-
if (tbmpre==NULL)
246-
{
247-
/* No more pages to prefetch */
248-
tbm_end_iterate(prefetch_iterator);
249-
node->prefetch_iterator=prefetch_iterator=NULL;
250-
break;
251-
}
252-
node->prefetch_pages++;
253-
PrefetchBuffer(scan->rs_rd,MAIN_FORKNUM,tbmpre->blockno);
254-
}
255-
}
256-
#endif/* USE_PREFETCH */
206+
BitmapPrefetch(node,scan);
257207

258208
/*
259209
* Okay to fetch the tuple
@@ -411,6 +361,84 @@ bitgetpage(HeapScanDesc scan, TBMIterateResult *tbmres)
411361
scan->rs_ntuples=ntup;
412362
}
413363

364+
/*
365+
*BitmapAdjustPrefetchIterator - Adjust the prefetch iterator
366+
*/
367+
staticinlinevoid
368+
BitmapAdjustPrefetchIterator(BitmapHeapScanState*node,
369+
TBMIterateResult*tbmres)
370+
{
371+
#ifdefUSE_PREFETCH
372+
TBMIterator*prefetch_iterator=node->prefetch_iterator;
373+
374+
if (node->prefetch_pages>0)
375+
{
376+
/* The main iterator has closed the distance by one page */
377+
node->prefetch_pages--;
378+
}
379+
elseif (prefetch_iterator)
380+
{
381+
/* Do not let the prefetch iterator get behind the main one */
382+
TBMIterateResult*tbmpre=tbm_iterate(prefetch_iterator);
383+
384+
if (tbmpre==NULL||tbmpre->blockno!=tbmres->blockno)
385+
elog(ERROR,"prefetch and main iterators are out of sync");
386+
}
387+
#endif/* USE_PREFETCH */
388+
}
389+
390+
/*
391+
* BitmapAdjustPrefetchTarget - Adjust the prefetch target
392+
*
393+
* Increase prefetch target if it's not yet at the max. Note that
394+
* we will increase it to zero after fetching the very first
395+
* page/tuple, then to one after the second tuple is fetched, then
396+
* it doubles as later pages are fetched.
397+
*/
398+
staticinlinevoid
399+
BitmapAdjustPrefetchTarget(BitmapHeapScanState*node)
400+
{
401+
#ifdefUSE_PREFETCH
402+
if (node->prefetch_target >=node->prefetch_maximum)
403+
/* don't increase any further */ ;
404+
elseif (node->prefetch_target >=node->prefetch_maximum /2)
405+
node->prefetch_target=node->prefetch_maximum;
406+
elseif (node->prefetch_target>0)
407+
node->prefetch_target *=2;
408+
else
409+
node->prefetch_target++;
410+
#endif/* USE_PREFETCH */
411+
}
412+
413+
/*
414+
* BitmapPrefetch - Prefetch, if prefetch_pages are behind prefetch_target
415+
*/
416+
staticinlinevoid
417+
BitmapPrefetch(BitmapHeapScanState*node,HeapScanDescscan)
418+
{
419+
#ifdefUSE_PREFETCH
420+
TBMIterator*prefetch_iterator=node->prefetch_iterator;
421+
422+
if (prefetch_iterator)
423+
{
424+
while (node->prefetch_pages<node->prefetch_target)
425+
{
426+
TBMIterateResult*tbmpre=tbm_iterate(prefetch_iterator);
427+
428+
if (tbmpre==NULL)
429+
{
430+
/* No more pages to prefetch */
431+
tbm_end_iterate(prefetch_iterator);
432+
node->prefetch_iterator=NULL;
433+
break;
434+
}
435+
node->prefetch_pages++;
436+
PrefetchBuffer(scan->rs_rd,MAIN_FORKNUM,tbmpre->blockno);
437+
}
438+
}
439+
#endif/* USE_PREFETCH */
440+
}
441+
414442
/*
415443
* BitmapHeapRecheck -- access method routine to recheck a tuple in EvalPlanQual
416444
*/

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