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From: legrand legrand <legrand_legrand@hotmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: Erratically behaving query needs optimization
Date: Thu, 22 Aug 2019 10:43:10 -0700 (MST)
Message-ID: <1566495790294-0.post@n3.nabble.com> (raw)
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	<9736f758-d702-ee9a-2988-53762c73c3e3@siscobra.com.br>
	<CAB14va_b+mCmZrp1R_FHgcp54HQ+Vq9e=MMg22DYLvWqb0XQTQ@mail.gmail.com>
	<827127b6-c034-b53b-5c2d-aa04743298d2@siscobra.com.br>
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	<de19053e-5d69-6bd9-0d48-62475283e8a4@siscobra.com.br>
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	<CAB14va9Mt4QVV_aR3rXxvaVyGNjB-5TpK6FSHAmdfMMu+PL-GA@mail.gmail.com>

Hello,

1/ access scheduler_task_executions 
	by index with device_id = 97
seems ok

2/ 
I don't understand why 
joining
scheduler_task_executions.id=scheduler_operation_executions.task_execution_id
is done using a parallel hash join 
when a nested loop would be better (regarding the number of rows involved)

maybe because index on scheduler_operation_executions.task_execution_id

    "index_task_execution_id_desc" btree (task_execution_id DESC NULLS LAST)

is not usable or bloated or because of DESC NULLS LAST ?


3/ join with results.operation_execution_id
	by index
seems OK

Regards
PAscal



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