Re: PATCH: Split stats file per database WAS: autovacuum stress-testing our system

Tom Lane escribió:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> >> Nice. Another interesting numbers would be device utilization, average
> >> I/O speed and required space (which should be ~2x the pgstat.stat size
> >> without the patch).
>
> > this point is important - with large warehouse with lot of databases
> > and tables you have move stat file to some ramdisc - without it you
> > lost lot of IO capacity - and it is very important if you need only
> > half sized ramdisc
>
> [ blink... ] I confess I'd not been paying close attention to this
> thread, but if that's true I'd say the patch is DOA. Why should we
> accept 2x bloat in the already-far-too-large stats file? I thought
> the idea was just to split up the existing data into multiple files.

I think they are saying just the opposite: maximum disk space
utilization is now half of the unpatched code. This is because when we
need to write the temporary file to rename on top of the other one, the
temporary file is not of the size of the complete pgstat data collation,
but just that for the requested database.

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Álvaro Herrera http://www.2ndQuadrant.com/
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