On 10/29/2018 04:17 PM, Andrew Gierth wrote:
"Tomas" == Tomas Vondra <tomas.von...@2ndquadrant.com> writes:
> On 10/26/2018 12:28 PM, Surafel Temesgen wrote:
>> hello ,
>>
>> The WITH TIES keyword is sql standard that specifies any peers of
>> retained rows to retained in the result set too .which means
>> according to ordering key the result set can includes additional rows
>> which have ties on the last position, if there are any and It work
>> with ORDER BY query.
Tomas> Thanks for the patch. I've looked at it today, and it seems
Tomas> mostly OK, with a couple of minor issues. Most of it is code
Tomas> formatting and comment wording issues, so I'm not going to go
Tomas> through them here - see the attached 0002 patch (0001 is your
Tomas> patch, rebased to current master).
I still think that this is the wrong approach. Implementing WITH TIES
and PERCENT together using an implicit window function call kills two
birds with one very small stone (the only executor change needed would
be teaching LIMIT to be able to stop on a boolean condition), with
maximum reuse of existing facilities.
Hmmm, maybe. How would that work, exactly? Wouldn't that mean extra
overhead (the window functions are hardly free) and limitations? Perhaps
that was discussed in some other thread in the past?
FWIW, I doubt the patch can be much smaller/simpler - a significant part
of the new stuff is in gram.y and node read/out infrastructure, the
changes to LIMIT node are fairly minimal.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
