| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Extended statistics is not working on Vars hidden under a RelabelType |
| Date: | 2017-10-12 13:43:47 |
| Message-ID: | CAKJS1f-89Yh-ZiaCK5YVEUu+TDNK058r3JAfL8N-dws_L84PEg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 13 October 2017 at 02:17, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> I propose this slightly larger change.
hmm, this is not right. You're not checking that there's a Var below
the RelabelType.
I tried with:
explain select * from ab where (a||a)::varchar = '' and b = '';
and your code assumed the OpExpr was a Var.
The reason Tomas coded it the way it was coded is due to the fact that
there's already code that works exactly the same way in
clauselist_selectivity(). Personally, I don't particularly like that
code, but I'd rather not invent a new way to do the same thing.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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