From: | Rick Otten <rottenwindfish(at)gmail(dot)com> |
---|---|
To: | yash mehta <yash215(at)gmail(dot)com> |
Cc: | Michael Lewis <mlewis(at)entrata(dot)com>, Flo Rance <trourance(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, pgsql-performance(at)lists(dot)postgresql(dot)org |
Subject: | Re: select distinct runs slow on pg 10.6 |
Date: | 2019-09-10 11:56:54 |
Message-ID: | CAMAYy4LPC1txNPDrvw8qU136hAj__0bBpVt-aYh38+jJ5POXog@mail.gmail.com |
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Lists: | pgsql-performance |
On Tue, Sep 10, 2019 at 12:53 AM yash mehta <yash215(at)gmail(dot)com> wrote:
> Hi Michael/Justin/Flo,
>
> Thank you all for your assistance. As Michael said, looks like there are
> no more tricks left.
>
> On Mon, Sep 9, 2019 at 9:09 PM Michael Lewis <mlewis(at)entrata(dot)com> wrote:
>
>> If you can't modify the query, then there is nothing more to be done to
>> optimize the execution afaik. Distinct is much slower than group by in
>> scenarios like this with many columns. You already identified the disk sort
>> and increased work mem to get it faster by 3x. There are not any other
>> tricks of which I am aware.
>>
>
Could you put a view in between the real table and the query that does the
group by ? (since you can't change the query)
I'm wondering if the sort/processing time would be faster when that
distinct is invoked if the rows are already distinct.
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