Connecting MapServer to a raster table in PostGIS

Question

I am new in MapServer and I want to visualize some raster tables in MapServer.

My mapfile is:

MAP
CONFIG "MS_ERRORFILE"  "error.log"
DEBUG 5
NAME "milad"
STATUS on
SIZE 600 600 
EXTENT -8321547  5668833  -7583277  6240180
UNITS meters


LAYER
    NAME "poly"
    STATUS DEFAULT
    TYPE RASTER

    DATA "PG:host=localhost port=5432 dbname=geodatabase user=postgres password=**** schema=public table=milad_raster column=st_asraster" 

    PROJECTION
        "init=epsg:3857"
    END 

    PROCESSING "NODATA=-9999"
    PROCESSING "SCALE=AUTO"


    CLASS
        STYLE
            COLOR 200 0 0
        END
    END
END

END

Then I use this URL to see the map but I see nothing. It is just the white screen.

http://localhost/cgi-bin/mapserv.exe?map=/ms4w/apps/milad/milad_raster.map&mode=map

I checked the log files and I saw that the error is:

[Thu Jan 23 15:34:58 2020].675000 
msLoadMap(): 0.016s
[Thu Jan 23 15:34:58 2020].675000 CGI Request 
1 on process 7144
[Thu Jan 23 15:34:58 2020].675000 
msDrawMap(): rendering using outputformat 
named png (AGG/PNG).
[Thu Jan 23 15:34:58 2020].675000 
msDrawMap(): WMS/WFS set-up and query, 0.000s
[Thu Jan 23 15:34:58 2020].675000 
msDrawRasterLayerLow(poly): entering.
[Thu Jan 23 15:34:58 2020].768000 Corrupt, 
empty or missing file 'PG:host=localhost 
port=5432 dbname=geodatabase user=postgres 
password=**** schema=public 
table=milad_raster column=st_asraster' for 
layer 'poly' ... ignoring this missing data.  
Error browsing database for PostGIS Raster 
properties
[Thu Jan 23 15:34:58 2020].768000 
msDrawMap(): Layer 0 (poly), 0.093s
[Thu Jan 23 15:34:58 2020].768000 
msDrawMap(): Drawing Label Cache, 0.000s
[Thu Jan 23 15:34:58 2020].768000 msDrawMap() 
total time: 0.093s
[Thu Jan 23 15:34:58 2020].768000 
msSaveImage(stdout) total time: 0.000s
[Thu Jan 23 15:34:58 2020].768000 mapserv 
request processing time (msLoadMap not 
incl.): 0.093s
[Thu Jan 23 15:34:58 2020].768000 
msFreeMap(): freeing map at 02648FD8.
[Thu Jan 23 15:34:58 2020].784000 mapserv 
total execution time: 0.125s

If you do not want to read that file, just read this one cuz error is here:

[Thu Jan 23 15:34:58 2020].768000 Corrupt, empty or missing file 'PG:host=localhost port=5436 dbname=geodatabase user=postgres password=**** schema=public table=milad_raster column=st_asraster' for layer 'poly' ... ignoring this missing data. Error browsing database for PostGIS Raster properties

I can visualize my raster table in QGIS. Thus, I believe it should be correct. I checked with gdalinfo and I was able to read the raster table. What is the problem? the URL? the mapfile? or something else?

Answer 1

I did some steps and with the help of @nmtoken I was able to fix it. I believe that my raster table had some problems maybe because I created it with complex geometries or maybe another reason. This time I changed the raster table I just simply used this codes in PostGIS to create a raster table from a single polygon:

SELECT ST_AsRaster(geom, 100, 100 , '8BSI', 100 , -99 ) AS rast
INTO raster_test
FROM polygon;

ALTER TABLE raster_test ADD COLUMN rid SERIAL PRIMARY KEY;

SELECT AddRasterConstraints('raster_test','rast');

Before, my table did not have rid and was created from complex geometries. Then, I used the following mapfile:

MAP
CONFIG "MS_ERRORFILE"  "error.log"
DEBUG 5
NAME "milad"
STATUS on
SIZE 600 600 
EXTENT -8321547  5668833  -7583277  6240180
UNITS meters

LAYER
    NAME "poly"
    STATUS DEFAULT
    TYPE RASTER
    CLASSITEM "[pixel]"
    DATA "PG:host=localhost port=5436 dbname=geodatabase user=postgres password=**** schema=public table=raster_test column=rast mode=2"      
    PROJECTION

        "init=epsg:3857"

    END 



    PROCESSING "SCALE=AUTO"
    CLASS
    EXPRESSION "0"
        STYLE
           COLOR 0 0 0
        END
    END

    CLASS
    EXPRESSION ([pixel] >= 64 AND [pixel] < 128)
        STYLE

            COLOR 200 0 0

        END
    END
END

END

Then, I used the following URL:

http://localhost/cgi-bin/mapserv.exe?map=/ms4w/apps/milad/milad_raster.map&mode=map

And it is the raster representation in browser:

I am not sure but I think my previous raster may had overlapping pixels in some areas.