Horton

Re: [HACKERS] Runtime Partition Pruning

David Rowley <david.rowley@2ndquadrant.com>

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From: David Rowley <david.rowley@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Beena Emerson <memissemerson@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, amul sul <sulamul@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2017-12-22T01:37:49Z
Lists: pgsql-hackers 
On 22 December 2017 at 14:29, Robert Haas <robertmhaas@gmail.com> wrote:
> On Thu, Dec 21, 2017 at 6:53 PM, David Rowley
> <david.rowley@2ndquadrant.com> wrote:
>> Are you considering some sort of clauselist_selectivity() estimate on
>> the given parameters and comparing that to the same selectivities that
>> were determined for the previous custom plans?
>
> No, I don't think comparing to previous custom plans is a workable
> approach.  I was thinking, rather, that if we know for example that
> we've doing pruning on partition_column = $1, then we know that only
> one partition will match.  That's probably a common case.  If we've
> got partition_column > $1, we could assume that, say, 75% of the
> partitions would match.  partition_column BETWEEN $1 and $2 is
> probably a bit more selective, so maybe we assume 50% of the
> partitions would match.

Okay. Do you think this is something we need to solve for this patch?
When I complained originally I didn't quite see any way to even test
the majority of this patch with the regression tests, but Beena has
since proven me wrong about that.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. Initialize ExprStates once in run-time partition pruning

  2. Add bms_prev_member function

  3. Support partition pruning at execution time

  4. Document partprune.c a little better

  5. Fix crash in pg_replication_slot_advance

  6. Add parallel-aware hash joins.

  7. Fix typo.

  8. Allow --with-bonjour to work with non-macOS implementations of Bonjour.

  9. Mention need for --no-inc-recursive in rsync command