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Commit35ac618

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Fix some oversights in BRIN patch.
Remove HeapScanDescData.rs_initblock, which wasn't being used for anythingin the final version of the patch.Fix IndexBuildHeapScan so that it supports syncscan again; the patchbroke synchronous scanning for index builds by forcing rs_startblkto zero even when the caller did not care about that and had askedfor syncscan.Add some commentary and usage defenses to heap_setscanlimits().Fix heapam so that asking for rs_numblocks == 0 does what you wouldreasonably expect. As coded it amounted to requesting a whole-tablescan, because those "--x <= 0" tests on an unsigned variable wouldbehave surprisingly.
1 parent29f171c commit35ac618

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3 files changed

+32
-14
lines changed

3 files changed

+32
-14
lines changed

‎src/backend/access/heap/heapam.c‎

Lines changed: 20 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -277,7 +277,6 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
277277
scan->rs_startblock=0;
278278
}
279279

280-
scan->rs_initblock=0;
281280
scan->rs_numblocks=InvalidBlockNumber;
282281
scan->rs_inited= false;
283282
scan->rs_ctup.t_data=NULL;
@@ -302,11 +301,22 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
302301
pgstat_count_heap_scan(scan->rs_rd);
303302
}
304303

304+
/*
305+
* heap_setscanlimits - restrict range of a heapscan
306+
*
307+
* startBlk is the page to start at
308+
* numBlks is number of pages to scan (InvalidBlockNumber means "all")
309+
*/
305310
void
306311
heap_setscanlimits(HeapScanDescscan,BlockNumberstartBlk,BlockNumbernumBlks)
307312
{
313+
Assert(!scan->rs_inited);/* else too late to change */
314+
Assert(!scan->rs_syncscan);/* else rs_startblock is significant */
315+
316+
/* Check startBlk is valid (but allow case of zero blocks...) */
317+
Assert(startBlk==0||startBlk<scan->rs_nblocks);
318+
308319
scan->rs_startblock=startBlk;
309-
scan->rs_initblock=startBlk;
310320
scan->rs_numblocks=numBlks;
311321
}
312322

@@ -477,7 +487,7 @@ heapgettup(HeapScanDesc scan,
477487
/*
478488
* return null immediately if relation is empty
479489
*/
480-
if (scan->rs_nblocks==0)
490+
if (scan->rs_nblocks==0||scan->rs_numblocks==0)
481491
{
482492
Assert(!BufferIsValid(scan->rs_cbuf));
483493
tuple->t_data=NULL;
@@ -511,7 +521,7 @@ heapgettup(HeapScanDesc scan,
511521
/*
512522
* return null immediately if relation is empty
513523
*/
514-
if (scan->rs_nblocks==0)
524+
if (scan->rs_nblocks==0||scan->rs_numblocks==0)
515525
{
516526
Assert(!BufferIsValid(scan->rs_cbuf));
517527
tuple->t_data=NULL;
@@ -651,7 +661,7 @@ heapgettup(HeapScanDesc scan,
651661
if (backward)
652662
{
653663
finished= (page==scan->rs_startblock)||
654-
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks<=0 : false);
664+
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks==0 : false);
655665
if (page==0)
656666
page=scan->rs_nblocks;
657667
page--;
@@ -662,7 +672,7 @@ heapgettup(HeapScanDesc scan,
662672
if (page >=scan->rs_nblocks)
663673
page=0;
664674
finished= (page==scan->rs_startblock)||
665-
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks<=0 : false);
675+
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks==0 : false);
666676

667677
/*
668678
* Report our new scan position for synchronization purposes. We
@@ -754,7 +764,7 @@ heapgettup_pagemode(HeapScanDesc scan,
754764
/*
755765
* return null immediately if relation is empty
756766
*/
757-
if (scan->rs_nblocks==0)
767+
if (scan->rs_nblocks==0||scan->rs_numblocks==0)
758768
{
759769
Assert(!BufferIsValid(scan->rs_cbuf));
760770
tuple->t_data=NULL;
@@ -785,7 +795,7 @@ heapgettup_pagemode(HeapScanDesc scan,
785795
/*
786796
* return null immediately if relation is empty
787797
*/
788-
if (scan->rs_nblocks==0)
798+
if (scan->rs_nblocks==0||scan->rs_numblocks==0)
789799
{
790800
Assert(!BufferIsValid(scan->rs_cbuf));
791801
tuple->t_data=NULL;
@@ -914,7 +924,7 @@ heapgettup_pagemode(HeapScanDesc scan,
914924
if (backward)
915925
{
916926
finished= (page==scan->rs_startblock)||
917-
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks<=0 : false);
927+
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks==0 : false);
918928
if (page==0)
919929
page=scan->rs_nblocks;
920930
page--;
@@ -925,7 +935,7 @@ heapgettup_pagemode(HeapScanDesc scan,
925935
if (page >=scan->rs_nblocks)
926936
page=0;
927937
finished= (page==scan->rs_startblock)||
928-
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks<=0 : false);
938+
(scan->rs_numblocks!=InvalidBlockNumber ?--scan->rs_numblocks==0 : false);
929939

930940
/*
931941
* Report our new scan position for synchronization purposes. We

‎src/backend/catalog/index.c‎

Lines changed: 10 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2168,7 +2168,8 @@ IndexBuildHeapScan(Relation heapRelation,
21682168
/*
21692169
* As above, except that instead of scanning the complete heap, only the given
21702170
* number of blocks are scanned. Scan to end-of-rel can be signalled by
2171-
* passing InvalidBlockNumber as numblocks.
2171+
* passing InvalidBlockNumber as numblocks. Note that restricting the range
2172+
* to scan cannot be done when requesting syncscan.
21722173
*/
21732174
double
21742175
IndexBuildHeapRangeScan(RelationheapRelation,
@@ -2251,7 +2252,14 @@ IndexBuildHeapRangeScan(Relation heapRelation,
22512252
allow_sync);/* syncscan OK? */
22522253

22532254
/* set our scan endpoints */
2254-
heap_setscanlimits(scan,start_blockno,numblocks);
2255+
if (!allow_sync)
2256+
heap_setscanlimits(scan,start_blockno,numblocks);
2257+
else
2258+
{
2259+
/* syncscan can only be requested on whole relation */
2260+
Assert(start_blockno==0);
2261+
Assert(numblocks==InvalidBlockNumber);
2262+
}
22552263

22562264
reltuples=0;
22572265

‎src/include/access/relscan.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -38,8 +38,8 @@ typedef struct HeapScanDescData
3838
/* state set up at initscan time */
3939
BlockNumberrs_nblocks;/* total number of blocks in rel */
4040
BlockNumberrs_startblock;/* block # to start at */
41-
BlockNumberrs_initblock;/*block # to consider initial of rel */
42-
BlockNumberrs_numblocks;/*number of blocks toscan */
41+
BlockNumberrs_numblocks;/*max number of blocks to scan */
42+
/*rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
4343
BufferAccessStrategyrs_strategy;/* access strategy for reads */
4444
boolrs_syncscan;/* report location to syncscan logic? */
4545

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