| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: why partition pruning doesn't work? |
| Date: | 2018-07-16 00:24:59 |
| Message-ID: | CAKJS1f_ZoH6vJwpiFt4EvE+BuCoDE=hLJZ_9o0TZfkrVXxpSRQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 16 July 2018 at 12:12, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sun, Jul 15, 2018 at 1:02 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> What we'd be better off doing, if we go this route, is to install an
>> assertion-build-only test that verifies during relation_open(NoLock)
>> that some kind of lock is already held on the rel. That would protect
>> not only the executor, but a boatload of existing places that open
>> rels with NoLock on the currently-unverified assumption that a lock is
>> already held.
>
> +1. In fact, maybe we ought to go a little further and have a
> relation_reopen(oid, mode) that verifies that a lock in the specified
> mode is held.
Wouldn't it be better to just store the Relation indexed by its relid
somewhere the first time we opened it? Then just do a direct array
lookup on that rather than looking up by hashtable in syscache?
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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