[postgis-users] polygon minimum width

[Simon Greener]

Surya,

Yes, SQL Analytics / Windowing functions are only available in version 8.4.

There are many methods for simulating a ROWNUMBER in Postgresql but, in this case, we could use the CTID field
to distinguish between the two rows.:

select CTID as rin, the_geom
   from River r
  where r.Name = 'Barito';

ctid;the_geom
tid;geometry
(0,1);"010200002000000000050000000000000000B06DC000000000005061C00000000000E053C00000000000803FC00000000000E05DC000000000006059400000000000C044400000000000D064400000000000C049C00000000000706F40"
(0,2);"0102000020000000000700000000000000004045400000000000F870400000000000106B4000000000007064400000000000A051400000000000205540000000000000124000000000000012C00000000000C043C00000000000404DC00000000000E053C00000000000F062C000000000004044C00000000000706EC0"


SELECT min(ST_Distance(l.the_geom,r.the_geom)) as Min_Width
   FROM (select ctid as rin, the_geom
           from River r
          where r.Name = 'Barito' ) as l,
        (select ctid as rin, the_geom
           from River r
          where r.Name = 'Barito' ) as r
  WHERE l.rin <> r.rin;

min_width
double precision
48.2597140480546

regards
Simon
-- 
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