| From: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
|---|---|
| To: | "mac_man2008(at)yahoo(dot)it" <mac_man2008(at)yahoo(dot)it> |
| Cc: | "Nicolas Barbier" <nicolas(dot)barbier(at)gmail(dot)com>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Sorting. When? |
| Date: | 2011-02-12 19:05:20 |
| Message-ID: | 4D568590020000250003A916@gw.wicourts.gov |
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| Lists: | pgsql-hackers |
"mac_man2008(at)yahoo(dot)it" <mac_man2008(at)yahoo(dot)it> wrote:
> So, invoking or not invoking sorting depends on different
> parameters of the specific DBMS, does it?
In the right circumstances (where autovacuum or other maintenance
jobs happen to run in the background at the right moment), two
back-to-back runs on the same database with no data or configuration
changes could do this differently. You wouldn't see that too often,
but if the estimated costs of sorting versus non-sorting plans were
close, the random sampling of one statistics sampling run versus
another could cause a change.
-Kevin
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