| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Simon Riggs <simon(at)2ndQuadrant(dot)com>, jd(at)commandprompt(dot)com, Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Do we still need constraint_exclusion? |
| Date: | 2009-01-07 22:46:01 |
| Message-ID: | 6731.1231368361@sss.pgh.pa.us |
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Bruce Momjian <bruce(at)momjian(dot)us> writes:
>> * Simon Riggs (simon(at)2ndQuadrant(dot)com) wrote:
>>> I don't really understand this. Who can set up an inherited table
>>> structure but can't remember to turn on constraint_exclusion?
> This new change also adds the constraint exclusion overhead only for
> inhertance (by default) so it should slightly improve query peformance.
Right, I think that's the real winning argument for having this: it
gets the benefit of c_e for partitioned tables without imposing overhead
for non-partitioned tables. See Josh B's remarks upthread about
actually going to the trouble of turning c_e off and on on-the-fly to
try to approximate that result.
regards, tom lane
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