| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Greg Stark <stark(at)mit(dot)edu> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: An idle thought |
| Date: | 2010-03-17 21:09:48 |
| Message-ID: | 1268860188.4053.489.camel@monkey-cat.sm.truviso.com |
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| Lists: | pgsql-hackers |
On Tue, 2010-03-16 at 15:29 +0000, Greg Stark wrote:
> I'm picturing storing a bit in the visibility map indicating that *no*
> records are visible in a given page.
I've been thinking for a while that we could store the visibility
information in a structure separate from the heap -- sort of like the
visibility map, but per-tuple and authoritative rather than a per-page
hint.
There are all kinds of challenges there, but it might be worth thinking
about. Visibility information is highly compressible, and requires
constant maintenance (updates, deletes, freezing, etc.). It also might
make it possible to move to 64-bit xids, if we wanted to.
Regards,
Jeff Davis
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