Horton

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

Douglas Doole <dougdoole@gmail.com>

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From: Douglas Doole <dougdoole@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>
Cc: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-08-24T17:07:37Z
Lists: pgsql-hackers 
>
> I don't greatly like the way that the regression test case filters
> the output; it hides too much IMO.  I'd be inclined to try to return
> the EXPLAIN output with as much detail preserved as possible.  Maybe
> we could use regex substitution on lines of the output to get rid of
> stuff that won't be invariant.
>

My first thought was to do a regex over the explain output to mask the
troublesome value, but I couldn't figure out how to make it work and didn't
find an example (admittedly didn't spent a huge amount of time hunting
though). I'd love to see how to put it together.

Doug
- Salesforce

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.