Re: UNION causes horrible plan on JOIN

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От Justin Pryzby
Тема Re: UNION causes horrible plan on JOIN
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Msg-id 20191028224553.GP23808@telsasoft.com
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Ответ на UNION causes horrible plan on JOIN  (Craig James <cjames@emolecules.com>)
Ответы Re: UNION causes horrible plan on JOIN
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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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