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Fix parallel index scan hang with deleted or half-dead pages.

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The previous coding forgot to release the scan before seizing
it again, leading to a lockup.

Report by Patrick Hemmer.  Diagnosis by Thomas Munro.  Patch by
Amit Kapila.

Discussion: http://postgr.es/m/CAEepm=2xZUcOGP9V0O_G0=2P2wwXwPrkF=upWTCJSisUxMnuSg@mail.gmail.com
This commit is contained in:
Robert Haas 2017-12-13 16:09:00 -05:00
parent 1d6fb35ad6
commit 884a60840c
1 changed files with 10 additions and 0 deletions
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10
src/backend/access/nbtree/nbtsearch.c
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@ -1486,6 +1486,11 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno, ScanDirection dir)
if (_bt_readpage(scan, dir, P_FIRSTDATAKEY(opaque))) if (_bt_readpage(scan, dir, P_FIRSTDATAKEY(opaque)))
break; break;
} }
else if (scan->parallel_scan != NULL)
{
/* allow next page be processed by parallel worker */
_bt_parallel_release(scan, opaque->btpo_next);
}
/* nope, keep going */ /* nope, keep going */
if (scan->parallel_scan != NULL) if (scan->parallel_scan != NULL)
@ -1581,6 +1586,11 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno, ScanDirection dir)
if (_bt_readpage(scan, dir, PageGetMaxOffsetNumber(page))) if (_bt_readpage(scan, dir, PageGetMaxOffsetNumber(page)))
break; break;
} }
else if (scan->parallel_scan != NULL)
{
/* allow next page be processed by parallel worker */
_bt_parallel_release(scan, BufferGetBlockNumber(so->currPos.buf));
}
/* /*
* For parallel scans, get the last page scanned as it is quite * For parallel scans, get the last page scanned as it is quite