[mapserver-users] MapServer failing to find any result, causing WMSGetFeatureInfo hang

[P Kishor]

Greetings,

I have a 1 km. sq. grid layer stored in Pg/PostGIS (8.4/1.4.0) served
by MapServer 5.4.2. If I query for WMSGetFeatureInfo (from OpenLayers
2.8) while zoomed out, the following queries run in the backend, and
xmin, xmax, ymin, ymax values are returned to the user and presented
in a popup window by OpenLayers.

statement 1a:
select encode(AsBinary(force_collection(force_2d("the_geom")),'NDR'),'base64')
as geom,"gid" from grid_1km_cnnf where the_geom &&
GeomFromText('POLYGON((630976.809608983
585638.303216044,630976.809608983 587492.192802734,632291.577207376
587492.192802734,632291.577207376 585638.303216044,630976.809608983
585638.303216044))',find_srid('','grid_1km_cnnf','the_geom'))

statement 1b:
select * from grid_1km_cnnf where false limit 0

statement 1c:
select "gid", "ID", "XMIN", "XMAX", "YMIN", "YMAX",
encode(AsBinary(force_collection(force_2d("the_geom")),'NDR'),'base64')
as geom,"gid" from grid_1km_cnnf where "gid" = 31437

Mapserver logs the following messages

[Mon Sep 21 18:58:04 2009].190912 CGI Request 1 on process 56359
[Mon Sep 21 18:58:04 2009].191385 msWMSLoadGetMapParams(): enabling
non-square pixels.
[Mon Sep 21 18:58:04 2009].301261 mapserv request processing time
(msLoadMap not incl.): 0.110s

My understanding is that statement 1a finds the actual grid square containing
my click, statement 1b returns no rows at all so I don't know what it
does, and statement 1c returns the actual attributes. All this happens
successfully.

Now, if I zoom in quite a bit and click for WMSGetFeatureInfo, the
only statement that runs is statement 2a below. As is evident from
MapServer logs shown below, no result is found, so my
WMSGetFeatureInfo event keeps on waiting for something to come back.

statement 2a:
select encode(AsBinary(force_collection(force_2d("the_geom")),'NDR'),'base64')
as geom,"gid" from grid_1km_cnnf where the_geom &&
GeomFromText('POLYGON((630616.805138803
580174.87136618,630616.805138803 580290.724370171,630699.037346471
580290.724370171,630699.037346471 580174.87136618,630616.805138803
580174.87136618))',find_srid('','grid_1km_cnnf','the_geom'))

MapServer log, as shown below, shows that no result was returned.

[Mon Sep 21 19:00:29 2009].391044 CGI Request 1 on process 56414
[Mon Sep 21 19:00:29 2009].391503 msWMSLoadGetMapParams(): enabling
non-square pixels.
[Mon Sep 21 19:00:29 2009].410388 msQueryByPoint(): Search returned no
results. No matching record(s) found.
[Mon Sep 21 19:00:29 2009].410501 mapserv request processing time
(msLoadMap not incl.): 0.019s


Now, statement 2a runs fine and fast in Pgadmin3, returns a gid, and I
can then use that gid to run the equivalent of statement 1c above and
get back the xmin, ymin, xmax, ymax attributes, but only through
pgadmin3. Through my map interface I get nothing back because nothing
happens after statement 2a.

I don't even know where the problem is -- doesn't seem like a problem
with OpenLayers because all it does is send a query. Doesn’t seem to
be a problem with Pg because if it actually got the query it would
return a result, as it does in Pgadmin3. But, why should it be a
problem with MapServer as all MapServer would do, if it got back a
result from 2a, it would run the equivalent of 1b and 1c.

As is, my query just hangs. Any idea what is going on?

Fwiw, I don't have TOLERANCE and TOLERANCEUNITS set in my mapfile, as,
from their description, they don't seem to apply. In any case, if not
provided, TOLERANCE defaults to 0 for poly layers which restricts poly
searches so that point falls within the polygon, which is what I want.

I am stumped.


-- 
Puneet Kishor http://www.punkish.org
Carbon Model http://carbonmodel.org
Charter Member, Open Source Geospatial Foundation http://www.osgeo.org
Science Commons Fellow, http://sciencecommons.org/about/whoweare/kishor
Nelson Institute, UW-Madison http://www.nelson.wisc.edu
-----------------------------------------------------------------------
Assertions are politics; backing up assertions with evidence is science
=======================================================================
Sent from Madison, WI, United States