| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, 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 17:18:54 |
| Message-ID: | 1174411134.23455.506.camel@dogma.v10.wvs |
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| Lists: | pgsql-hackers |
On Tue, 2007-03-20 at 09:03 +0000, Simon Riggs wrote:
> 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.
>
I think it would be a good first step if we could just keep stats on
multiple columns in the same table. If we can do more than that, great.
We could probably keep stats on multiple columns across different
tables, but I don't know how those statistics should be used. Using
statistics to estimate joins seems like a tricky problem. Maybe it's
already solved with known algorithms?
Regards,
Jeff Davis
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