Re: [HACKERS] Mapping MERGE onto CTEs (Re: MERGE SQL Statement for PG11)

[Craig Ringer]

On 2 November 2017 at 01:14, Alvaro Herrera  wrote:
> Nico Williams wrote:
>
>> As an aside, I'd like to be able to control which CTEs are view-like and
>> which are table-like.  In SQLite3, for example, they are all view-like,
>> and the optimizer will act accordingly, whereas in PG they are all
>> table-like, and thus optimizer barriers.
>
> There was a short and easy to grasp (OK, maybe not) discussion on the
> topic of CTEs acting differently.  I think the consensus is that for
> CTEs that are read-only and do not use functions that aren't immutable,
> they may be considered for inlining.
> https://www.postgresql.org/message-id/5351711493487...@web53g.yandex.ru

Yep. All theoretical though, I don't think anyone (myself included)
stumped up a patch.


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 Craig Ringer   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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Re: [HACKERS] Mapping MERGE onto CTEs (Re: MERGE SQL Statement for PG11)

[Alvaro Herrera]

Nico Williams wrote:

> As an aside, I'd like to be able to control which CTEs are view-like and
> which are table-like.  In SQLite3, for example, they are all view-like,
> and the optimizer will act accordingly, whereas in PG they are all
> table-like, and thus optimizer barriers.

There was a short and easy to grasp (OK, maybe not) discussion on the
topic of CTEs acting differently.  I think the consensus is that for
CTEs that are read-only and do not use functions that aren't immutable,
they may be considered for inlining.
https://www.postgresql.org/message-id/5351711493487...@web53g.yandex.ru

-- 
Álvaro Herrerahttps://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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