[Labs-l] Tool labs replicas are missing the indexes?

Wed Nov 12 15:32:21 UTC 2014

Thanks Antoine, I was using the test more for educational purposes but
Brion's poist is a good reminder not to use page_random for any serious
sampling purpose

G


Giovanni Luca Ciampaglia

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2014-11-12 4:00 GMT-05:00 Antoine Musso <hashar+wmf at free.fr>:

> Le 11/11/2014 14:36, Brad Jorsch (Anomie) a écrit :
> > On Tue, Nov 11, 2014 at 1:02 AM, Giovanni Luca Ciampaglia
> <snip>
> > >   Drawing a list of random titles with page_random takes more than a
> > >   minute!
> >
> >
> > Because you're doing it wrong. "page_random > rand()" evaluates rand()
> > *for each row*. Since it's nowhere near constant, it can't use an index.
> <snip>
>
> Hello,
>
> Grabbing random pages is a bit of madness which has long confused
> people. Brion Vibber wrote a nice explanations a few years ago that
> gives a good overview:
>
> https://brionv.com/log/2007/11/22/random-tests/
>
> --
> Antoine "hashar" Musso
>
>
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