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Re: Sorting Tuples

From: "Sean Davis" <sdavis2(at)mail(dot)nih(dot)gov>
To: Manolo <manolo(dot)espa(at)gmail(dot)com>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: Sorting Tuples
Date: 2008-03-13 12:32:36
Message-ID: 264855a00803130532x207e6af9v6bc221b986b0b472@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-novice
On Thu, Mar 13, 2008 at 7:25 AM, Manolo <manolo(dot)espa(at)gmail(dot)com> wrote:
> Hi to all.
>
>  INTRODUCTION:
>  I created a patch for PostgreSQL even if i'm not a PostgreSQL user. I
>  just wanted to implement an idea for possibly getting better External
>  Sorting module on PostgreSQL just using some basic C programming
>  knowledge and now I'm facing to using PostgreSQL for a while in order to
>  test my patch.
>  My patch "activates" when user is trying to sort a load of data more or
>  less twice bigger than his available memory (e.g.: sorting 5GB of data
>  just disposing of 1GB of available memory)
>
>  PROBLEM:
>  First of all I want to realise my patch does sorts correctly or not. But
>  it's a little bit difficult to check when
>
>         SELECT * FROM huge_table ORDER BY a_column_of_huge_table;
>
>  means checking a 4 or 5 GB result...
>
>  QUESTION:
>  Is there a way to discover if data is sorted correctly other than
>  spending 2 months taking a look to the 5 GB result tuples, one by one?

I can think of a couple of answers:

1) test your sorting routine on smaller data sets

2) have an external program verify the sort result on larger sets

The bigger question is what you hope to accomplish.  In other words,
what about postgresql sorting doesn't work for you?

Sean

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