Horton

Re: [PATCH] Push limit to sort through a subquery

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Douglas Doole <dougdoole@gmail.com>
Cc: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-08-21T18:43:05Z
Lists: pgsql-hackers 
On Fri, Aug 18, 2017 at 4:08 PM, Douglas Doole <dougdoole@gmail.com> wrote:
>> 4. I am pretty doubtful that "Memory: 25kB" is going to be stable
>> enough for us to want that output memorialized in the regression ...
>
> Fair enough. I wanted to be a bit more sophisticated in my check than
> looking for a single value so I worked out something that distills the
> explain down to the key elements.

Works for me.  While I'm sure this won't eclipse previous achievements
in this area, it still seems worthwhile.  So committed with one minor
change to shorten a long-ish line.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Propagate sort instrumentation from workers back to leader.

  2. Push tuple limits through Gather and Gather Merge.

  3. Code review for pushing LIMIT through subqueries.

  4. Make new regression test case parallel-safe, and improve its output.

  5. Push limit through subqueries to underlying sort, where possible.

  6. Move targetlist SRF handling from expression evaluation to new executor node.