| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Amit Langote <amitlangote09(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] path toward faster partition pruning |
| Date: | 2018-04-03 21:47:58 |
| Message-ID: | CAKJS1f_7S389iuqhxR=pm6mEXztGF0fRBzSqmFjoU52SfCvonQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 4 April 2018 at 00:02, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)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.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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