Horton

Re: Add proper planner support for ORDER BY / DISTINCT aggregates

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Dean Rasheed <dean.a.rasheed@gmail.com>, Ronan Dunklau <ronan.dunklau@aiven.io>, Justin Pryzby <pryzby@telsasoft.com>, Pavel Luzanov <p.luzanov@postgrespro.ru>, pgsql-hackers@lists.postgresql.org, Ranier Vilela <ranier.vf@gmail.com>
Date: 2023-01-17T07:05:19Z
Lists: pgsql-hackers 
Richard Guo <guofenglinux@gmail.com> writes:
> BTW, I wonder if we should have checked CoercionForm before
> fix_upper_expr_mutator steps into CoerceViaIO->arg to adjust the expr
> there.

I will just quote what it says in primnodes.h:

 * NB: equal() ignores CoercionForm fields, therefore this *must* not carry
 * any semantically significant information.

If you think the planner should act differently for different values of
CoercionForm, you are mistaken.  Maybe this is evidence of some
previous bit of brain-fade, but if so we need to fix that.

			regards, tom lane

Commits

  1. Don't presort ORDER BY/DISTINCT Aggrefs with volatile functions

  2. Add enable_presorted_aggregate GUC

  3. Remove pessimistic cost penalization from Incremental Sort

  4. Fix hypothetical problem passing the wrong GROUP BY pathkeys

  5. Remove unused fields from ExprEvalStep

  6. Improve performance of ORDER BY / DISTINCT aggregates

  7. Refactor function parse_subscription_options.