[postgis-users] duplicated nodes

Olivier Leprêtre o.lepretre at gmail.com
Wed Aug 2 12:28:18 PDT 2017



I have a point layer that contains several superposed nodes two, three times
or more. I would like to display each group list and the number of item in
each. I found this query which “works” but returns some false positive


select case when lag(o.geom) OVER (PARTITION BY o.geom) = o.geom then ''
else 'x ' || o.nbre::text end,d.code from

(select geom,count(*) as nbre from nodes group by geom having count(*) >1)
as o,

lateral (select * from nodes) as d where st_within(o.geom,d.geom)


I understand that false positives (yellow beneath) comes  from “group by
geom” which use a bounding box and catch close but not duplicated points.



I tried other solutions which all get too complicated with several “join of
join”. I would appreciate if someone has an idea on the top of his/her head






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