RE: HASH GROUP BY
- From: "Rob Dempsey" <Rob.Dempsey@xxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 25 Apr 2008 16:51:28 +0100
Hi
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.
Rob
Ps there is another bug in 10.2.0.1 and 10.2.0.2 Bug number 6471770
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Elliott, Patrick
Sent: 23 April 2008 22:08
To: david@xxxxxxxxxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: HASH GROUP BY
I stand corrected. These are some serious bugs!
Pat
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of David Aldridge
Sent: Wednesday, April 23, 2008 3:38 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: HASH GROUP BY
There have also been a few genuine bugs as well -- I'm using it in
10.2.0.2 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" <patrick.elliott@xxxxxxxxxxxxx>
To: "Elliott, Patrick" <patrick.elliott@xxxxxxxxxxxxx>;
"Rob.Dempsey@xxxxxxxxxx" <Rob.Dempsey@xxxxxxxxxx>;
"oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
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.
Pat
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Elliott, Patrick
Sent: Wednesday, April 23, 2008 1:44 PM
To: Rob.Dempsey@xxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: HASH GROUP BY
This is enabled by default in version 9.2.0.5 and up. Are you
explicitly disabling it in your environment?
Pat
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Rob Dempsey
Sent: Wednesday, April 23, 2008 12:08 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: HASH GROUP BY
Hi
Our current Oracle version -> 10.2.0.1
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)
Rob
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