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Re: efficient data reduction (and deduping)

From: Claudio Freire <klaussfreire(at)gmail(dot)com>
To: Alessandro Gagliardi <alessandro(at)path(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: efficient data reduction (and deduping)
Date: 2012-03-01 19:39:12
Message-ID: CAGTBQpaBKj8e8wrBrF8+HjNyNKOrJrCBqdCyj1ZR+3ssXjK3sQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Thu, Mar 1, 2012 at 4:35 PM, Alessandro Gagliardi
<alessandro(at)path(dot)com> wrote:
> Interesting solution. If I'm not mistaken, this does solve the problem of
> having two entries for the same user at the exact same time (which violates
> my pk constraint) but it does so by leaving both of them out (since there is
> no au1.hr_timestamp > au2.hr_timestamp in that case). Is that right?

Yes, but it would have to be same *exact* time (not same hour).

You can use more fields to desambiguate too, ie:

au1.hr_timestamp > au2.hr_timestamp or (au1.hr_timestamp ==
au2.hr_timestamp and au1.some_other_field > au2.some_other_field)

If you have a sequential id to use in desambiguation, it would be best.

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