Re: BUG #15287: postgres_fdw: the "WHERE date_trunc('day', dt) = 'YYYY-MM-DD' does not push to remote.

On Fri, Jul 20, 2018 at 2:28 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

>
> However, that could only fix the OP's problem for these particular
> functions, which are a small fraction of the ones we have that take
> collatable types but don't really care about collation. I kinda feel
> like we should have invented an "ignores collation" function property,
> so that such functions could be identified --- that would not only let
> postgres_fdw handle this honestly, but we could refrain from throwing
> unmatched-collations errors for cases where it doesn't really matter.
> Maybe it's not too late to invent that in future. If the parser sets
> inputcollid = 0 for any function marked that way, then if the function is
> incorrectly marked as ignoring collation it would get an error at runtime,
> so it seems like we could add it safely.
>

Would this automatically apply to operators as well, like hstore's ->
operator, once the fetchval function was marked? The non-shippability of
that can be a major problem.

Cheers,

Jeff