| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Should we add GUCs to allow partition pruning to be disabled? |
| Date: | 2018-05-10 14:49:31 |
| Message-ID: | 20180510144931.i3b3xom6bbt3bif6@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Robert Haas wrote:
> In defense of constraint exclusion, let me note that constraint
> exclusion is not restricted to inheritance cases. It could eliminate
> the need to scan a completely unpartitioned table if the WHERE clause
> can be refuted by CHECK constraints. It could eliminate the need to
> scan some partitions of a partitioned table based on whatever
> additional CHECK constraints exist beyond the partitioning
> constraints.
This is a great point that hadn't occurred to me. It means that we
should keep constraint exclusion on its own <sect2> rather than relegate
it to <sect3>, as my proposed patch does. I think it's a good idea to
add this point there too.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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