| From: | Csaba Nagy <ncslists(at)googlemail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Tomas Vondra <tv(at)fuzzy(dot)cz>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: estimating # of distinct values |
| Date: | 2011-01-05 13:43:06 |
| Message-ID: | 1294234986.3889.22.camel@clnt-sysecm-cnagy |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Thu, 2010-12-30 at 21:02 -0500, Tom Lane wrote:
> How is an incremental ANALYZE going to work at all?
How about a kind of continuous analyze ?
Instead of analyzing just once and then drop the intermediate results,
keep them on disk for all tables and then piggyback the background
writer (or have a dedicated process if that's not algorithmically
feasible) and before writing out stuff update the statistics based on
the values found in modified buffers. Probably it could take a random
sample of buffers to minimize overhead, but if it is done by a
background thread the overhead could be minimal anyway on multi-core
systems.
Not sure this makes sense at all, but if yes it would deliver the most
up to date statistics you can think of.
Cheers,
Csaba.
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