| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Beena Emerson <memissemerson(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, amul sul <sulamul(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] Runtime Partition Pruning |
| Date: | 2017-12-21 23:53:33 |
| Message-ID: | CAKJS1f8q_d7_Viweeivt1eS4Q8a0WAGFbrgeX38468mVgKseTA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 22 December 2017 at 12:45, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> PREPARE q3 (int, int) AS SELECT * FROM unpartitioned_table WHERE
> partkey BETWEEN $1 AND $2;
>
> ...that has to decide whether to use an index. And to do that it has
> to estimate what fraction of the table will match the BETWEEN clause.
> That may be an uninformed guess, but it guesses something. We
> probably want to do something here that makes the guess for a
> partitioned_table similar to the guess for an unpartitioned_table.
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?
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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