Re: SQL:2011 application time

On 11/4/24 13:16, Sam Gabrielsson wrote:
> Foreign key violation errors are incorrectly raised in a few cases for a temporal foreign key with
> default ON UPDATE NO ACTION. Test is based on the commited v39 patches (used a snapshot version of
> PG18 devel available from PGDG).

Thank you for the report! I confirmed that this is a problem. In ri_restrict we fail if any fk
records still match the being-changed pk, but for temporal if you're merely shrinking the pk range,
fk references could still wind up being valid (if you're only shrinking it a little). So we need to
do more work.

> In the temporal NO ACTION case something similar to this (though with appropriate locks) could
> perhaps be tested in ri_restrict (when ri_Check_Pk_Match returns false):
>
>   SELECT 1
>   FROM (SELECT range_agg(pkperiodatt) AS r
>       FROM <pktable>
>       WHERE pkatt1 = $1 [AND ...]
>       AND pkperiodatt && $n) AS pktable,
>     (SELECT fkperiodatt AS r
>       FROM <fktable>
>       WHERE fkatt1 = $1 [AND ...]
>       AND fkperiodatt && $n) AS fktable
>   WHERE NOT fktable.r <@ pktable.r

This solution looks like it will work to me. Basically: find FKs that still match the PK, but only
fail if they are no longer covered.

IIRC for RESTRICT it is *correct* to reject the change, so we would want to keep the old SQL there,
and only update it for NOACTION.

I'll work on a fix and submit another set of patches.

Yours,

--
Paul ~{:-)
pj(at)illuminatedcomputing(dot)com