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Gsoc2012 idea, tablesample

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Joshua Berkus <josh(at)agliodbs(dot)com>
Cc: Qi Huang <huangqiyx(at)hotmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, andres(at)anarazel(dot)de, alvherre(at)commandprompt(dot)com, neil conway <neil(dot)conway(at)gmail(dot)com>, daniel(at)heroku(dot)com, cbbrowne(at)gmail(dot)com, kevin grittner <kevin(dot)grittner(at)wicourts(dot)gov>
Subject: Gsoc2012 idea, tablesample
Date: 2012-04-17 06:16:29
Message-ID: 4F8D0ABD.4080403@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 24.03.2012 22:12, Joshua Berkus wrote:
> Qi,
>
> Yeah, I can see that.  That's a sign that you had a good idea for a project, actually: your idea is interesting enough that people want to debate it.  Make a proposal on Monday and our potential mentors will help you refine the idea.

Yep. The discussion withered, so let me try to summarize:

1. We probably don't want the SQL syntax to be added to the grammar. 
This should be written as an extension, using custom functions as the 
API, instead of extra SQL syntax.

2. It's not very useful if it's just a dummy replacement for "WHERE 
random() < ?". It has to be more advanced than that. Quality of the 
sample is important, as is performance. There was also an interesting 
idea of on implementing monetary unit sampling.

I think this would be a useful project if those two points are taken 
care of.

Another idea that Robert Haas suggested was to add support doing a TID 
scan for a query like "WHERE ctid<  '(501,1)'". That's not enough work 
for GSoC project on its own, but could certainly be a part of it.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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