Useless sort by

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi all,
I have a view v_table defined as following:

select a,b,c,d,e,f
from  t_table
sort by  a,b,c;

the usage pattern of this view is the following:

select distinct(a) from v_table;
select distinct(b) from v_table where a = "XXX";
select distinct(c) from v_table where a = "XXX" and b = "YYYY";

because of that sort in the view definition the first query above
takes not less than 3 seconds. I have solved this performance issue
removing the sort from the view definition and putting it in the
select reducing the time from > 3secons to < 150ms.

Can not the optimizer take rid of that useless sort on those
kind of queries ?


Regards
Gaetano Mendola




-- 
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance


[Postgresql General]     [Postgresql PHP]     [PHP Users]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Yosemite]

  Powered by Linux