Re: Free WAL caches on switching segments - Mailing list pgsql-patches

From Bruce Momjian
Subject Re: Free WAL caches on switching segments
Date
Msg-id 200602131813.k1DIDwk03860@candle.pha.pa.us
Whole thread Raw
In response to Re: Free WAL caches on switching segments  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Free WAL caches on switching segments
List pgsql-patches
Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Tom Lane wrote:
> >> Depending on OS features we have never depended on before is a *huge*
> >> ongoing maintenance cost, and I have not seen an argument that I think
> >> justifies this one.
>
> > I disagree.  It is a localized change and seems like a win, and it uses
> > a standard POSIX feature, rather than an OS-specific one.
>
> It's still gonna need a configure test and so on.  "POSIX" does not mean
> "exists everywhere".  Moreover, the submitter has not even proven that
> the code works (or even builds, much less does anything useful) on the
> platforms it's supposedly for.

The submitter believes the C macro test is sufficient:

    I think we can use _POSIX_ADVISORY_INFO to test if posix_fadvise exists.
    Also, I added the check on whether WAL archiving is enabled, because
    archivers might use the caches to read the WAL segment.

I assume if it follows the POSIX spec it will work on all platforms that
support this feature.

--
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  pgman@candle.pha.pa.us               |  (610) 359-1001
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