On 4 April 2018 at 09:47, David Rowley <david.rowley@2ndquadrant.com> wrote:
> On 4 April 2018 at 00:02, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote:
>> But actually, the presence of only Params in the pruning steps should
>> result in the pruning not being invoked at all (at least for the static
>> pruning case), thus selecting all partitions containing non-null data. It
>> is better to implement that instead of a workaround like scan_all_nonnulls
>> side-channel I was talking about.
>
> I don't think this is quite true. Since we're only using strict
> clauses, a list of quals with just Params still means that NULLs can't
> match. If you skip the step altogether then won't you have you've lost
> the chance at pruning away any NULL-only partition?
>
> I think it would be better to just have special handling in
> get_matching_list_bound so that it knows it's performing <>
> elimination. I'd thought about passing some other opstrategy but the
> only safe one I thought to use was InvalidStrategy, which is already
> used by NULL handling.
I'm currently working up a patch to do this the way I think is best.
I'll submit it soon and we can review and get your thoughts on it.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
