| From: | "Zeugswetter Andreas ADI SD" <Andreas(dot)Zeugswetter(at)s-itsolutions(dot)at> |
|---|---|
| To: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: HOT line pointer bloat and PageRepairFragmentation |
| Date: | 2007-09-13 16:52:48 |
| Message-ID: | E1539E0ED7043848906A8FF995BDA579025C5D36@m0143.s-mxs.net |
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> The COLD updated (old) tuple would be pruned to dead line pointer
> once the tuple becomes DEAD. Normally that would let us reuse the
> tuple storage for other purposes. We do the same for DELETEd tuples.
Oh, I thought only pruned tuples from HOT chains can produce a
"redirect dead" line pointer.
This looks like a problem, since we might end up with a page filled with
LP_DEAD slots, that all have no visibility info and can thus not be
cleaned
by vacuum.
Maybe PageRepairFragmentation when called from HOT should prune less
aggressively. e.g. prune until a max of 1/2 the available slots are
LP_DEAD,
and not prune the rest.
Andreas
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