Re: effective_cache_size cfg

From: Scott Ribe <scott_ribe(at)elevated-dev(dot)com>
To: "Ghiurea, Isabella" <Isabella(dot)Ghiurea(at)nrc-cnrc(dot)gc(dot)ca>
Cc: "pgsql-admin(at)postgresql(dot)org" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: effective_cache_size cfg
Date: 2018-10-15 20:03:11
Message-ID: 8564EC49-A9D1-42BD-90E9-215467441DC8@elevated-dev.com
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>
> On Oct 15, 2018, at 12:04 PM, Ghiurea, Isabella <Isabella(dot)Ghiurea(at)nrc-cnrc(dot)gc(dot)ca> wrote:
>
> I am running PGSQL 10.4 on Cent OS Pg instance has ' effective_cache_size' parameter not enabled I would like to learn what will the optimizer behavior be in this case ?
> ( default is set to 4GB , I was thinking PG 's optimizer will try to use all available OS RAM when trying to estimate a query, is this the case)

That's merely a hint to the optimizer as to how much file data is likely to be cached by the OS--it doesn't directly affect any PG allocations, rather it might influence PG's choice of steps to carry out a query, which of course could indirectly change the RAM that PG would use.

--
Scott Ribe
scott_ribe(at)elevated-dev(dot)com
https://www.linkedin.com/in/scottribe/

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