| From: | Richard Huxton <dev(at)archonet(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, 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 09:30:54 |
| Message-ID: | 45FFA9CE.8010305@archonet.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Simon Riggs wrote:
> 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.
This is one hint I think everyone can agree on. Being able to say that
values in different columns are related just gives the planner more
information to work with.
--
Richard Huxton
Archonet Ltd
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Martijn van Oosterhout | 2007-03-20 10:22:42 | Re: Buildfarm feature request: some way to track/classify failures |
| Previous Message | Simon Riggs | 2007-03-20 09:03:58 | Re: Stats for multi-column indexes |