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Prevent index-only scans from returning wrong answers under Hot Standby.

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The alternative of disallowing index-only scans in HS operation was
discussed, but the consensus was that it was better to treat marking
a page all-visible as a recovery conflict for snapshots that could still
fail to see XIDs on that page.  We may in the future try to soften this,
so that we simply force index scans to do heap fetches in cases where
this may be an issue, rather than throwing a hard conflict.
This commit is contained in:
Robert Haas
2012-04-26 20:00:21 -04:00
parent 92df220343
commit 3424bff90f
7 changed files with 36 additions and 11 deletions
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src/include/access/visibilitymap.h
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@@ -25,7 +25,7 @@ extern void visibilitymap_pin(Relation rel, BlockNumber heapBlk,
Buffer *vmbuf);
extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf);
extern void visibilitymap_set(Relation rel, BlockNumber heapBlk,
XLogRecPtr recptr, Buffer vmbuf);
XLogRecPtr recptr, Buffer vmbuf, TransactionId cutoff_xid);
extern bool visibilitymap_test(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
extern BlockNumber visibilitymap_count(Relation rel);
extern void visibilitymap_truncate(Relation rel, BlockNumber nheapblocks);