Re: Global temporary tables

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
Cc: Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Global temporary tables
Date: 2019-08-19 15:53:27
Message-ID: CAFj8pRAFbHvdOTyOjB2utcBQDojXBr+Uuw+yWRCsz9Rv7GYJhg@mail.gmail.com
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> Certainly, default (small) temp buffer size plays roles.
> But it this IPC host this difference is not so important.
> Result with local temp tables and temp_buffers = 1GB: 859k TPS.
>

It is little bit unexpected result.I understand so it partially it is
generic problem access to smaller dedicated caches versus access to bigger
shared cache.

But it is hard to imagine so access to local cache is 10% slower than
access to shared cache. Maybe there is some bottle neck - maybe our
implementation of local buffers are suboptimal.

Using local buffers for global temporary tables can be interesting from
another reason - it uses temporary files, and temporary files can be
forwarded on ephemeral IO on Amazon cloud (with much better performance
than persistent IO).

>
> --
>
> Konstantin Knizhnik
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company
>
>

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