Re: UNION causes horrible plan on JOIN - Mailing list pgsql-performance

From Justin Pryzby
Subject Re: UNION causes horrible plan on JOIN
Date
Msg-id 20191028224553.GP23808@telsasoft.com
Whole thread Raw
In response to UNION causes horrible plan on JOIN  (Craig James <cjames@emolecules.com>)
Responses Re: UNION causes horrible plan on JOIN
List 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



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