Re: UNION causes horrible plan on JOIN

From: Justin Pryzby <pryzby(at)telsasoft(dot)com>
To: Craig James <cjames(at)emolecules(dot)com>
Cc: pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: Re: UNION causes horrible plan on JOIN
Date: 2019-10-28 22:45:53
Message-ID: 20191028224553.GP23808@telsasoft.com
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-performance

On Mon, Oct 28, 2019 at 03:40:58PM -0700, Craig James wrote:
> On Postgres 9.6 (config below), I have a case I don't understand: three
> tables that can be separately queried in milliseconds, but when put
> together into one view using UNION, take 150 seconds to query. Here's the
> rough idea (actual details below):

Do you want UNION ALL ?

UNION without ALL distintifies the output.
https://www.postgresql.org/docs/current/sql-select.html#SQL-UNION

Justin

In response to

Responses

Browse pgsql-performance by date

  From Date Subject
Next Message Craig James 2019-10-28 23:30:24 Re: UNION causes horrible plan on JOIN
Previous Message Craig James 2019-10-28 22:40:58 UNION causes horrible plan on JOIN