Re: IMMUTABLE and PARALLEL SAFE function markings

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От Andres Freund
Тема Re: IMMUTABLE and PARALLEL SAFE function markings
Дата
Msg-id 20181126233940.hxnpwubssyf7eax4@alap3.anarazel.de
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Ответ на Re: IMMUTABLE and PARALLEL SAFE function markings  (Vik Fearing <vik.fearing@2ndquadrant.com>)
Ответы Re: IMMUTABLE and PARALLEL SAFE function markings
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Hi,

On 2018-11-27 00:33:10 +0100, Vik Fearing wrote:
> On 26/11/2018 22:23, Gajus Kuizinas wrote:
> > I was wondering what is the reason IMMUTABLE functions are not by
> > default PARALLEL SAFE and if the default behaviour could be changed to
> > make IMMUTABLE functions PARALLEL SAFE?
> 
> I think I have to concur with this.  When is an immutable function not
> parallel safe?
> 
> Sure it could be mislabeled as immutable but it could just as easily be
> mislabeled as parallel safe.  And we already treat fake immutable
> functions as user errors, for example in indexes.

I think it'd introduce more problems than it'd solve. Either you ignore
the proparallel setting - resulting in broken catalog querying - or you
have to have a decent amount of special behaviour that an explicit ALTER
FUNCTION ... IMMUTABLE | STABLE | VOLATILE and SET PARALLEL { UNSAFE
| RESTRICTED | SAFE } would also need to change the respective other
category.

Greetings,

Andres Freund


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