| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Should we add GUCs to allow partition pruning to be disabled? |
| Date: | 2018-05-18 20:02:18 |
| Message-ID: | CA+TgmobsTkQs6Xt3=TjVThRWwm4=9Or7LF0owoqS7LbC+uyS2Q@mail.gmail.com |
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On Fri, May 18, 2018 at 4:22 AM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Yeah, I think it'd help to have Append be annotated as suggested by Robert
> above. I guess if "at executor startup" is shown, then the subnodes
> listed under Append will consist of only those that survived
> executor-startup pruning and thus will help understand why there are fewer
> than shown with EXPLAIN (without ANALYZE). Also, if "at runtime" is
> shown, a user may want look at nloops property of the individual subnodes
> to guess at how much pruning has occurred; although only the latter (that
> is, inspecting nloops) suffices to know that runtime pruning has occurred
> as also currently written in the documentation about pruning [1], the
> first piece of information (the "at runtime" annotation) seems nice to have.
Having EXPLAIN and EXPLAIN ANALYZE show different things doesn't sound
like a good idea.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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