| From: | "Simon Riggs" <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | "Mark Kirkwood" <markir(at)paradise(dot)net(dot)nz> |
| Cc: | "Jeff Davis" <pgsql(at)j-davis(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Stats for multi-column indexes |
| Date: | 2007-03-20 09:03:58 |
| Message-ID: | 1174381438.4160.857.camel@silverbirch.site |
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| Lists: | pgsql-hackers |
On Tue, 2007-03-20 at 14:14 +1200, Mark Kirkwood wrote:
> Jeff Davis wrote:
> >
> > I know we can't keep stats on every combination of columns. My initial
> > idea would be to only keep stats about a multi-column index (and
> > probably optional for those, too).
> >
>
> Maybe you would want to keep single column indexes too, so that (more)
> accurate estimates for bitmap-and type plans are possible.
We should allow the DBA to specify which groups of cols to keep
statistics on, if there is no index on that group.
That solves the combinatorial explosion problem.
--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com
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