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Re: Sorting Tuples

From: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
To: Manolo <manolo(dot)espa(at)gmail(dot)com>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: Sorting Tuples
Date: 2008-03-13 15:11:32
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Lists: pgsql-novice
On Thu, Mar 13, 2008 at 7:25 AM, Manolo <manolo(dot)espa(at)gmail(dot)com> wrote:
>  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)

OK, we kinda already have that covered.

>  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...

5GB is nothing, but I'll continue...

>  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'm trying to understand this.  You wrote a patch to improve external
sorting... and, you're not sure how to test whether it sorted
correctly?  I don't mean to be rude, but am I missing something here?

To your question, just sort the output and run checksums against the
output for comparison.

Jonah H. Harris, Sr. Software Architect | phone: 732.331.1324
EnterpriseDB Corporation | fax: 732.331.1301
499 Thornall Street, 2nd Floor | jonah(dot)harris(at)enterprisedb(dot)com
Edison, NJ 08837 |

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