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Re: Gsoc2012 Idea --- Social Network database schema

From: Neil Conway <neil(dot)conway(at)gmail(dot)com>
To: Qi Huang <huangqiyx(at)hotmail(dot)com>
Cc: daniel(at)heroku(dot)com, josh(at)agliodbs(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Gsoc2012 Idea --- Social Network database schema
Date: 2012-03-20 21:12:45
Message-ID: CAOW5sYbYMVf80r5rd4uh=XbKpt5iKYHgADhVsaqrzZr65Lb06w@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2012/3/19 Qi Huang <huangqiyx(at)hotmail(dot)com>:
>> I actually tried to find out, personally...not sure if I was searching
>> wrongly, but searching for TABLESAMPLE did not yield a cornucopia of
>> useful conversations at the right time in history (~2007), even when
>> the search is given a broad date-horizon (all), so I, too, an
>> uninformed as to the specific objections.
>>
>> http://www.postgresql.org/search/?m=1&q=TABLESAMPLE&l=&d=-1&s=d
>
> I sent a mail to Nail Conway asking him about this. Hope he could give a
> good answer.

I never tried to get TABLESAMPLE support into the main PostgreSQL tree
-- I just developed the original code as an exercise for the purposes
of the talk. Implementing TABLESAMPLE would probably be a reasonable
GSoc project.

My memory of the details is fuzzy, but one thing to check is whether
the approach taken by my patch (randomly choose heap pages and then
return all the live tuples in a chosen page) actually meets the
standard's requirements -- obviously it is not true that each heap
page has the same number of live tuples, so you aren't getting a truly
random sample.

Neil

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