Horton

Re: Optimze usage of immutable functions as relation

Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>

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From: Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>
To: Tom Lane <tgl@sss.pgh.pa.us>, Aleksandr Parfenov <asp437@gmail.com>
Cc: a.bykov@postgrespro.ru, pgsql-hackers@lists.postgresql.org, Antonin Houska <ah@cybertec.at>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2019-03-20T16:58:21Z
Lists: pgsql-hackers

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On 11/16/18 22:03, Tom Lane wrote:
> A possible fix for this is to do eval_const_expressions() on
> function RTE expressions at this stage (and then not need to
> do it later), and then pull up only when we find that the
> RTE expression has been reduced to a single Const.


Attached is a patch that does this, and transforms RTE_FUCTION that was 
reduced to a single Const into an RTE_RESULT.

Not sure it does everything correctly, but some basic cases work. In 
particular, I don't understand whether it needs any handling of "append 
relations".


-- 
Alexander Kuzmenkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Commits

  1. Prevent bogus pullup of constant-valued functions returning composite.

  2. Allow functions-in-FROM to be pulled up if they reduce to constants.