Re: SELECT statement returns in 10seconds, but INSERT/CREATE TABLE AS with same SELECT takes 7 minutes

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Subject: Re: SELECT statement returns in 10seconds, but INSERT/CREATE TABLE AS with same SELECT takes 7 minutes
From: Tom Lane <tgl@xxxxxxxxxxxxx>
Date: Thu, 27 Sep 2018 16:41:29 -0400
Cc: ranade@xxxxxxxxxxxxxxxxx, pgsql-performance@xxxxxxxxxxxxxx
Comments: In-reply-to Vladimir Ryabtsev <greatvovan@xxxxxxxxx> message dated "Thu, 27 Sep 2018 13:39:32 -0700"
In-reply-to: <CAMqTPq=5KVOSKaxry0PFA8wVQWN8WsdycM=FSy1CUPUuGbDv7w@mail.gmail.com>
References: <CANrrCRxsC3wr711bjAJ4zK_16vF-qQHZXjSJTstbQt9kG5QDSw@mail.gmail.com> <24273.1538068894@sss.pgh.pa.us> <CAMqTPq=5KVOSKaxry0PFA8wVQWN8WsdycM=FSy1CUPUuGbDv7w@mail.gmail.com>

Vladimir Ryabtsev <greatvovan@xxxxxxxxx> writes:
>> The reason for the plan shape difference is probably that the bare SELECT
>> is allowed to use parallelism while INSERT/SELECT isn't.

> In case parallelism is used, should it report in the plan as something like
> "workers planned: N"?

It did --- see the Gather node.

			regards, tom lane

Follow-Ups:
- Re: SELECT statement returns in 10seconds, but INSERT/CREATE TABLE AS with same SELECT takes 7 minutes
  - From: Vladimir Ryabtsev

References:
- SELECT statement returns in 10seconds, but INSERT/CREATE TABLE AS with same SELECT takes 7 minutes
  - From: Arjun Ranade
- Re: SELECT statement returns in 10seconds, but INSERT/CREATE TABLE AS with same SELECT takes 7 minutes
  - From: Tom Lane
- Re: SELECT statement returns in 10seconds, but INSERT/CREATE TABLE AS with same SELECT takes 7 minutes
  - From: Vladimir Ryabtsev

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