From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Manfred Koizar <mkoi-pg(at)aon(dot)at> |
Cc: | Vivek Khera <khera(at)kcilink(dot)com>, pgsql-general(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Decent VACUUM (was: Buglist) |
Date: | 2003-08-21 21:56:02 |
Message-ID: | 28813.1061502962@sss.pgh.pa.us |
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Lists: | pgsql-general pgsql-hackers |
Manfred Koizar <mkoi-pg(at)aon(dot)at> writes:
> Good point. What about: Whenever a backend *deletes* a tuple it
> inserts a reference to its page into the RSM? Then an entry in the
> RSM doesn't necessarily mean that the referenced page has reclaimable
> space, but it would still be valueable information.
That might work if the RSM were lossless, but in practice I think it'd
have to be lossy, like the FSM. Which would mean that you'd still have
to do full-scan vacuums fairly regularly to make sure you hadn't
forgotten any freeable tuples. Conceivably it could be a win, though,
if you could do frequent "vacuum decent"s and only a full-scan vacuum
once in awhile (once a day maybe).
regards, tom lane
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