| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> |
| Cc: | amul sul <sulamul(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Antonin Houska <ah(at)cybertec(dot)at>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] advanced partition matching algorithm for partition-wise join |
| Date: | 2019-07-19 13:43:54 |
| Message-ID: | CA+TgmoY_Doe6bn3MD_f=EB7KO7tVsJKJK9r0aH_7KVLDnwGWTQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jul 18, 2019 at 2:55 AM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> I.e., partition_bounds_merge() is performed for each pair of input
> partitioned relations for a join relation in try_partitionwise_join().
> Since partition_bounds_merge() would need a lot of CPU cycles, I don't
> think this is acceptable; ISTM that some redesign is needed to avoid
> this. I'm wondering that once we successfully merged partition bounds
> from a pair of input partitioned relations for the join relation, by
> using the merged partition bounds, we could get the lists of matching
> to-be-joined partitions for subsequent pairs of input partitioned
> relations for the join relation in a more efficient way than by
> performing partition_bounds_merge() as proposed in the patch.
I don't know whether partition_bounds_merge() is well-implemented; I
haven't looked. But in general I don't see an alternative to doing
some kind of merging on each pair of input relations. That's just how
planning works, and I don't see why it should need to be prohibitively
expensive. I might be missing something, though; do you have an idea?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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