| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Zeugswetter Andreas ADI SD" <Andreas(dot)Zeugswetter(at)s-itsolutions(dot)at> |
| Cc: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: HOT line pointer bloat and PageRepairFragmentation |
| Date: | 2007-09-14 04:20:56 |
| Message-ID: | 20296.1189743656@sss.pgh.pa.us |
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"Zeugswetter Andreas ADI SD" <Andreas(dot)Zeugswetter(at)s-itsolutions(dot)at> writes:
> ...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.
No, it's the other way round: an LP_DEAD item pointer can *always* be
cleaned by VACUUM. It would not have become LP_DEAD unless someone had
confirmed that the pointed-to tuple was no longer visible to anyone.
The only reason we have LP_DEAD at all is that we don't want HOT pruning
to be required to remove the index entries that link to the item pointer.
regards, tom lane
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