Hi Thanks a lot for your help everybody.
Lars ________________________________ From: postgis-users <[email protected]> on behalf of Martin Davis <[email protected]> Sent: Thursday, April 11, 2019 10:03 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] diffrent execution plan on Postgres 9.5 and Postgres 11 for ST_union and performance problem Postgres 11 Well, we have figured out what the problem is - it's a known regression in the GEOS UnaryUnion code, reported in this ticket [1] Unfortunately there's no fix for this yet, but we'll try and escalate this. [1] https://trac.osgeo.org/geos/ticket/867 On Thu, Apr 11, 2019 at 11:07 AM Martin Davis <[email protected]<mailto:[email protected]>> wrote: On Thu, Apr 11, 2019 at 3:27 AM Lars Aksel Opsahl <[email protected]<mailto:[email protected]>> wrote: Can it be problem related ST_Union and aggregate ? Can you test the performance of aggregate ST_Union on it's own by dropping the GROUP BY and instead using a WHERE clause to union a small-ish subset of the geometries? (But large enough to give a measurable query time.)
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