Thank you all for your replies.
So, is there any precise way to discover when sorting is invoked?
Thanks.
Regards.
Fava
Il 11/02/2011 01:17, Robert Haas ha scritto:
On Thu, Feb 10, 2011 at 6:21 PM, Nicolas Barbier
<nicolas.barb...@gmail.com> wrote:
2011/2/10 mac_man2...@yahoo.it<mac_man2...@yahoo.it>:
Which operations invoke the sorting algorithms implemented in the sorting
module (tuplesort.c) ?
Of course, one of those operations invoking sorting is the ORDER BY clause
and the DISTINCT too.
Moreover, the Merge Join should be implemented invoking sorting.
Is there any other operation invoking sorting?
AFAIK, all set operators except for UNION ALL. (I am probably missing
a whole boatload of other things.)
Merge joins don't necessarily involve a sort - you could do a merge
over a pair of index scans, for example.
Set operations can be implemented using hashing or sorting, too.
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