I'm confused, can anyone help?
I want a random subset of features returned each call from a postgis table via
a wfs layer. I thought a simple SQL could do this pretty easily, but it doesn't
work from mapserver.
The mapfile data statement:
DATA "geom_ll from (select gid, geom_ll, name, random() as rand
from coast_poly
order by rand
limit 1) as foo using unique gid using srid=4326"
This returns 0 features.
If I change the query to order by gid it works fine & returns 1 feature.
If I retain order by rand but with no limit it works fine & returns all the
features.
If I paste the queries into a psql terminal, all instances work fine: eg:
select gid, name, random() as rand from coast_poly order by rand limit 1;
gid | name | rand
-----+--------------+-------------------
1 | NORTH ISLAND | 0.409694513771683
(1 row)
But I cannot get mapserver WFS output to work with both a random order & a
limit:
Source for this layer:
http://localhost/cgi-bin/mapserv?map=/srv/www/htdocs/map_nz/nz_wms_server.map&SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=nz_land
The number of features in this layer: 0
More confusing is that the WFS extent is correct for the feature that is not
there:
Extents:
In layer spatial reference system units : xMin,yMin 172.643,-41.6138 :
xMax,yMax 178.551,-34.3934
& worse, a data statement of:
DATA "geom_ll from (select gid, geom_ll, name, random() as rand
from coast_poly
where gid = 3 or gid=1
order by rand
limit 2) as foo using unique gid using srid=4326"
sometimes returns 1 & sometimes 0 features (but should return 2), as a wfs
layer, but as an sql in psql always returns the correct two features, but
varies the order, as you'd expect:
corax=# select gid, name, random() as rand
from coast_poly
where gid = 3 or gid=1
order by rand
limit 2;
gid | name | rand
-----+----------------+-------------------
3 | STEWART ISLAND | 0.102461547125131
1 | NORTH ISLAND | 0.609191857278347
(2 rows)
corax=# select gid, name, random() as rand
from coast_poly
where gid = 3 or gid=1
order by rand
limit 2;
gid | name | rand
-----+----------------+-------------------
1 | NORTH ISLAND | 0.531711789779365
3 | STEWART ISLAND | 0.784405956044793
(2 rows)
Thanks in advance,
Brent Wood
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