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From: Laurenz Albe <[email protected]>
To: Igor Korot <[email protected]>
To: pgsql-generallists.postgresql.org <[email protected]>
Subject: Re: Another documentation issue
Date: Wed, 23 Apr 2025 09:16:23 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+FnnTxPHoCZz2JBFxC3Wdsce9KUwNL0KcH5Ua37R55XLQbrpg@mail.gmail.com>
References: <CA+FnnTxPHoCZz2JBFxC3Wdsce9KUwNL0KcH5Ua37R55XLQbrpg@mail.gmail.com>

On Wed, 2025-04-23 at 00:21 -0500, Igor Korot wrote:
> On the page https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-SEQ-PAGE-COST
> 
> it is only given the default value of this parameter.
> 
> No min/max values are provided..
> 
> The same can be sad about
> https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-RANDOM-PAGE-COST

Sad.  But you can interpret it as "there is no maximum".  The actual maximum is DBL_MAX,
the biggest double precision value that your system can handle, and may depend on your
architecture.

> However, this page
> https://www.postgresql.org/docs/current/runtime-config-resource.html#GUC-EFFECTIVE-IO-CONCURRENCY
> describes both default and mn/max, however t s says:
> 
> [quote]
> The default is 1 on supported systems, otherwise 0
> [/quote]]
> 
> No explanation of what is "supported system" is given...
> 
> And the same can be said about
> https://www.postgresql.org/docs/current/runtime-config-resource.html#GUC-MAINTENANCE-IO-CONCURRENCY.

According to the source, it is "systems that have posix_fadvise()".  We could document that,
but I don't know if it would help many people.  I am not sure how easy and feasible it is
to research which versions of which operating systems qualify.

Yours,
Laurenz Albe

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