Re: BUG #16158: Check constraints using SQL functions work incorrectly

On Tue, Dec 10, 2019 at 5:28 AM PG Bug reporting form <
[email protected]> wrote:

> The following bug has been logged on the website:
>
> Bug reference:      16158
> Logged by:          Piotr Jander
> Email address:      [email protected]
> PostgreSQL version: 11.5
> Operating system:   x86_64 GNU/Linux
> Description:
>
> [...]

>
> My conjecture is that the bug is due to the use of SQL functions in the
> check.
> However, the
> [docs](https://www.postgresql.org/docs/9.4/ddl-constraints.html)
> on constraints do not mention any limitations on using such SQL functions
> in
> checks. If such limitations exist, they should be mentioned in the docs.
>

You should read the most current version of the documentation for a feature
before reporting a bug.  In this case the warnings you desired have been
added to more recently versions of the documentation.

https://www.postgresql.org/docs/12/ddl-constraints.html

Short answer, check constraints are designed to work only with data present
on the table upon which they are defined.  Use triggers to work with other
tables.

David J.