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* CHECK constraints - order of evaluation
@ 2020-05-14 09:06 PG Doc comments form <noreply@postgresql.org>
2020-05-14 14:40 ` Re: CHECK constraints - order of evaluation David G. Johnston <david.g.johnston@gmail.com>
0 siblings, 1 reply; 2+ messages in thread
From: PG Doc comments form @ 2020-05-14 09:06 UTC (permalink / raw)
To: pgsql-docs@lists.postgresql.org; +Cc: llucenic@gmail.com
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/9.6/ddl-constraints.html
Description:
I think the information about the "order of execution" when checking CHECK
constraints when inserting or updating records is missing in the
documentation.
There seems to be an old e-mail thread on the topic, however, there is no
information on whether the patch submitted was already merged and if so, in
which version of PostgreSQL.
I also suggest it would be good to point out in the documentation how the
order of CHECK constraints is created when there are more column CHECK
constraints and table CHECK constraints (i.e. in mixed cases) or whether
only the name of the constraint is relevant when it comes to it, not its
type (column/table).
Thank you very much in advance.
Kindest regards,
Ľudovít
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: CHECK constraints - order of evaluation
2020-05-14 09:06 CHECK constraints - order of evaluation PG Doc comments form <noreply@postgresql.org>
@ 2020-05-14 14:40 ` David G. Johnston <david.g.johnston@gmail.com>
0 siblings, 0 replies; 2+ messages in thread
From: David G. Johnston @ 2020-05-14 14:40 UTC (permalink / raw)
To: llucenic@gmail.com; pgsql-docs@lists.postgresql.org
On Thu, May 14, 2020 at 2:30 AM PG Doc comments form <noreply@postgresql.org>
wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/9.6/ddl-constraints.html
> Description:
>
> I think the information about the "order of execution" when checking CHECK
> constraints when inserting or updating records is missing in the
> documentation.
Check constraints require immutable functions and do not have side
effects. The order of their execution is immaterial and thus not
documented. The server is free to do whatever it wishes whenever it wishes
and users should not depend on any specific observed order in their usage
(I don't believe we actually say to avoid depending upon undocumented
behavior but that is the general guideline or working with systems).
David J.
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