From: Rob Dempsey <>
Date: Fri, 25 Apr 2008 16:51:28 +0100
Message-ID: <>


Thanks for the replies and apologies I was rather vague in my email.  

I am aware that HASH GROUP BY would not return the results in the correct order and that you need to use ORDER BY (not use the output of SORT GROUP BY)   I was more concerned with the bugs returning incorrect answer (Bug 4604970) , so examples  

At the moment I have explicity set _gby_hash_aggregation_enabled=FALSE.  


Ps there is another bug in and Bug number 6471770  

[] On Behalf Of Elliott, Patrick
Sent: 23 April 2008 22:08
To:; Subject: RE: HASH GROUP BY  

I stand corrected. These are some serious bugs!  


[] On Behalf Of David Aldridge
Sent: Wednesday, April 23, 2008 3:38 PM
Subject: Re: HASH GROUP BY

There have also been a few genuine bugs as well -- I'm using it in and haven't seen any issues though.  

Searching the metalink bug database for
_gby_hash_aggregation_enabled=false generally shows them.

  • Original Message ---- From: "Elliott, Patrick" <> To: "Elliott, Patrick" <>; "" <>; "" <> Sent: Wednesday, April 23, 2008 3:20:58 PM Subject: RE: HASH GROUP BY

Now I understand what you mean by buggy. It no longer sorts the rows. If you have code that relies on a group by being in sorted order, then the code will no longer work. If you have had to disable this in the past to get correct results, then you will need to continue disabling it indefinitely. The only way to fix it and reenable the hashing group by is to change the code.  

select column_a, column_b, count(column_c)

from table_abc

group by column_a, column_b

order by column_a, column_b  

You need to add the order by above to your code where you just had the "group by" alone before.  


[] On Behalf Of Elliott, Patrick
Sent: Wednesday, April 23, 2008 1:44 PM
To:; Subject: RE: HASH GROUP BY

This is enabled by default in version and up. Are you explicitly disabling it in your environment?  


[] On Behalf Of Rob Dempsey
Sent: Wednesday, April 23, 2008 12:08 PM To:


Our current Oracle version ->  

Does anyone know what version this feature has been fixed in. I would like to enable the feature, but it seems to have been very buggy (especially with wrong results)  


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Received on Fri Apr 25 2008 - 10:51:28 CDT

Original text of this message