| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
| Cc: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, pgsql-hackers Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [Proposal] Make the optimiser aware of partitions ordering |
| Date: | 2017-09-26 12:56:08 |
| Message-ID: | CA+TgmoYQcwL6wDdDM4qTkftB7CsgZXOYtPMrHe2sor2TCX1rkw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Sep 23, 2017 at 6:29 AM, Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
> That's true, but numCols, sortColdIdx etc are also used to display the
> sort key in an explain. If an append can return sorted data, it
> should also display the sort information, so I think these fields are
> still required in an Append node.
I don't think so. An index scan doesn't output that information, nor
does a nested loop which inherits a sort order from its outer path. I
think the rule is that a plan node which takes steps to get the data
into a certain order might want to output something about that, but a
plan node which somehow gets that ordering without taking any explicit
action doesn't print anything.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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