2015-03-18 14:31 GMT-03:00 Vivekanand Joshi <vjo...@zetainteractive.com>:
> So, here is the first taste of success and which gives me the confidence > that if properly worked out with a good hardware and proper tuning, > PostgreSQL could be a good replacement. > > Out of the 9 reports which needs to be migrated in PostgreSQL, 3 are now > running. > > Report 4 was giving an issue and I will see it tomorrow. > > Just to inform you guys that, the thing that helped most is setting > enable_nestloops to false worked. Plans are now not miscalculated. > > > > > Regards, > Vivek > > -----Original Message----- > From: pgsql-performance-ow...@postgresql.org > [mailto:pgsql-performance-ow...@postgresql.org] On Behalf Of Tomas Vondra > Sent: Tuesday, March 17, 2015 9:00 PM > To: pgsql-performance@postgresql.org > Subject: Re: [PERFORM] Performance issues > > On 17.3.2015 16:24, Thomas Kellerer wrote: > > Tomas Vondra schrieb am 17.03.2015 um 15:43: > >> On 17.3.2015 15:19, Thomas Kellerer wrote: > >>> Tomas Vondra schrieb am 17.03.2015 um 14:55: > >>>> (2) using window functions, e.g. like this: > >>>> > >>>> SELECT * FROM ( > >>>> SELECT *, > >>>> ROW_NUMBER() OVER (PARTITION BY touchpoint_execution_id > >>>> ORDER BY FROM max_creation_dt) AS rn > >>>> FROM s_f_touchpoint_execution_status_history > >>>> ) foo WHERE rn = 1 > >>>> > >>>> But estimating this is also rather difficult ... > >>> > >>> > >>> From my experience rewriting something like the above using DISTINCT > >>> ON is usually faster. > >> > >> How do you get the last record (with respect to a timestamp column) > >> using a DISTINCT ON? > > > > You need to use "order by ... desc". See here: > > http://sqlfiddle.com/#!15/d4846/2 > > Nice, thanks! > > > > > Btw: your row_number() usage wouldn't return the "latest" row either. > > It would return the "oldest" row. > > Oh, right. I forgot the DESC in the window. > > > -- > Tomas Vondra http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance > "But this is not a production-suitable setting. So what do you think how to get a work around this?" What about creating a read-only replica and apply this setting there?
