| From: | Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Greg Stark <stark(at)mit(dot)edu>, decibel <decibel(at)decibel(dot)org>, Josh Berkus <josh(at)agliodbs(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Multi-pass planner |
| Date: | 2013-04-04 18:53:18 |
| Message-ID: | m2ip42qg9t.fsf@2ndQuadrant.fr |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> for estimate_worstcase_fraction. So, when computing the cost of a
> path, we'd compute our current expected-case estimate, and also a
> worst-case estimate, and then compute the final cost as:
There also was the idea for the executor to be able to handle alternate
plans and some heuristic to determine that the actual cost of running a
plan is much higher than what's been estimated, so much so as to switch
to starting from scratch with the other plan instead.
Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
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