Re: [PERFORM] select with max functions

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От Mariel Cherkassky
Тема Re: [PERFORM] select with max functions
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Msg-id CA+t6e1=9if3_zd734XkBFY7xiS_OosE2t9sSK3JgPav_E9RgNA@mail.gmail.com
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Ответ на Re: [PERFORM] select with max functions  (Andreas Kretschmer <andreas@a-kretschmer.de>)
Ответы Re: [PERFORM] select with max functions
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Andreas I tried to rewrite it with the function rank() but I failed. The query you wrote isnt the same as what I search. Moreover, I cant use explain analyze because it is taking to much time to run and I'm getting timeout..

2017-10-01 21:48 GMT+03:00 Andreas Kretschmer <andreas@a-kretschmer.de>:


Am 01.10.2017 um 14:41 schrieb Mariel Cherkassky:
Hi,
I need to use the max function in my query. I had very bad performance when I used the max  :

               SELECT Ma.User_Id,
                      COUNT(*) COUNT
               FROM   Manuim Ma
               WHERE  Ma.Bb_Open_Date  =
                                  (SELECT max(Bb_Open_Date)
                                   FROM  Manuim Man
                                   WHERE Man.User_Id = Ma.User_Id
                                  )
               GROUP  BY Ma.User_Id
               HAVING COUNT(*) > 1;


Any idea how can I continue from here ? Thanks , Mariel.


Maybe you can rewrite it, for instance to

select distinct on (user_id, bb_open_date) user_id, bb_open_date, count(1) from Manuim group by 1,2 having count(1) > 1;

maybe much cheaper, but untested! If not, please share more details, at least table-definition.

Regards, Andreas

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