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Fix lazy_scan_heap so that it won't mark pages all-frozen too soon.

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Commit a892234f83 added a new bit per
page to the visibility map fork indicating whether the page is
all-frozen, but incorrectly assumed that if lazy_scan_heap chose to
freeze a tuple then that tuple would not need to later be frozen
again. This turns out to be false, because xmin and xmax (and
conceivably xvac, if dealing with tuples from very old releases) could
be frozen at separate times.

Thanks to Andres Freund for help in uncovering and tracking down this
issue.
This commit is contained in:
Robert Haas
2016-06-15 14:23:39 -04:00
parent c7a25c242f
commit 38e9f90a22
3 changed files with 40 additions and 16 deletions
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3
src/include/access/heapam_xlog.h
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@ -386,7 +386,8 @@ extern XLogRecPtr log_heap_freeze(Relation reln, Buffer buffer,
extern bool heap_prepare_freeze_tuple(HeapTupleHeader tuple,
TransactionId cutoff_xid,
TransactionId cutoff_multi,
xl_heap_freeze_tuple *frz);
xl_heap_freeze_tuple *frz,
bool *totally_frozen);
extern void heap_execute_freeze_tuple(HeapTupleHeader tuple,
xl_heap_freeze_tuple *xlrec_tp);
extern XLogRecPtr log_heap_visible(RelFileNode rnode, Buffer heap_buffer,