Re: Looks heap_create_with_catalog ignored the if_not_exists options - Mailing list pgsql-hackers

From Andy Fan
Subject Re: Looks heap_create_with_catalog ignored the if_not_exists options
Date
Msg-id CAKU4AWqENDfGP3mi605WF9pxMQin_x8AveWXG3C-Yx=bvFONUg@mail.gmail.com
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In response to Re: Looks heap_create_with_catalog ignored the if_not_exists options  (Michael Paquier <michael@paquier.xyz>)
Responses Re: Looks heap_create_with_catalog ignored the if_not_exists options
List pgsql-hackers
Thank you Michael!

 What can I do if I'm sure I will not use the CTAS creation ?   Take a look at the "heap_create_with_catalog" function, it check it and raise error.   Even I  change it to  "check it && if_not_existing",  raise error, it is still be problematic since we may some other session create between the check and the real creation end.   

Looks we need some locking there, but since PG is processes model,  I even don't know how to sync some code among processes in PG (any hint on this will be pretty good as well).

On Fri, Mar 1, 2019 at 8:35 PM Michael Paquier <michael@paquier.xyz> wrote:
On Fri, Mar 01, 2019 at 07:17:04PM +0800, Andy Fan wrote:
> for a createStmt,  it will call transformCreateStmt,  and then
> heap_create_with_catalog.
> but looks it just check the if_not_exists in transformCreateStmt.
>
> is it designed as this on purpose or is it a bug?

That's a bug.  Andreas Karlsson and I have been discussing it a couple
of days ago actually:
https://www.postgresql.org/message-id/20190215081451.GD2240@paquier.xyz

Fixing this is not as straight-forward as it seems, as it requires
shuffling a bit the code related to a CTAS creation so as all code
paths check at the same time for an existing relation.  Based on my
first impressions, I got the feeling that it would be rather invasive
and not worth a back-patch.
--
Michael

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