| From: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | David Wheeler <dwheeler(at)dgitsystems(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)lists(dot)postgresql(dot)org, Cameron Redpath <credpath(at)dgitsystems(dot)com> |
| Subject: | Re: Slow planning, fast execution for particular 3-table query |
| Date: | 2019-11-07 00:18:38 |
| Message-ID: | 20191107001838.GG4999@telsasoft.com |
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| Thread: | |
| Lists: | pgsql-performance |
On Thu, Nov 07, 2019 at 01:15:30PM +1300, David Rowley wrote:
> On Thu, 7 Nov 2019 at 11:59, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> >
> > On Mon, Nov 04, 2019 at 03:04:45AM +0000, David Wheeler wrote:
> > > Postgres version 9.5.19
> > > Each of the tables has between 3-4 indexes, and all the indexes include tid as first parameter.
>
> > But note that index definition will be prohibited since:
> >
> > https://www.postgresql.org/docs/9.6/release-9-6.html
> > |Disallow creation of indexes on system columns, except for OID columns (David Rowley)
> > |Such indexes were never considered supported, and would very possibly misbehave since the system might change the system-column fields of a tuple without updating indexes. However, previously there were no error checks to prevent them from being created.
>
> David will have meant the user column named "tid" rather than the
> system column named "ctid".
Ah. And David must have meant David W :)
Justin
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