Trying to insert geometry in existing table (geom field stay empty) using PostGIS?

Question

I'm trying to insert a new line in a big table with the following SQL using PostgreSQL 9.3 and PostGis 2.1.3:

INSERT INTO "Edigeo"."GEOM"(
            cnig, geom_surf,  
           etat, codcom)
    VALUES  ('H_11_4_6',
        ST_Difference((SELECT "GEOM_1".geom_surf FROM "Edigeo"."GEOM" AS "GEOM_1" WHERE "GEOM_1".codcom = '73101' AND "GEOM_1".cnig = 'H_1_6_0' LIMIT 1),(SELECT ST_Union("GEOM_2".geom_surf) FROM "Edigeo"."GEOM" AS "GEOM_2" WHERE "GEOM_2".codcom = '73101' AND "GEOM_2".cnig IN ('H_11_4_0','D_1_0_8')  AND ST_IsValid("GEOM_2".geom_surf) = True)),
        NULL,
        '73101')

my text field are filled without problem but i have an issue to fill the geometry column (geom_surf) with the ST_Difference statement... It remains empty in the table after the execution.

If i do the same in a select statement, the geometry seems ok.

SELECT ST_Difference((SELECT "GEOM_1".geom_surf FROM "Edigeo"."GEOM" AS "GEOM_1" WHERE "GEOM_1".codcom = '73101' AND "GEOM_1".cnig = 'H_1_6_0' LIMIT 1),(SELECT ST_Union("GEOM_2".geom_surf) FROM "Edigeo"."GEOM" AS "GEOM_2" WHERE "GEOM_2".codcom = '73101' AND "GEOM_2".cnig IN ('H_11_4_0','D_1_0_8')  AND ST_IsValid("GEOM_2".geom_surf) = True))

returns

So it looks nice.

But in my table after the insert:

Is there an issue with my geometry? or something else? I don't understand why it's not working...

Answer 1

For large geometries pgAdmin will show a blank field even though there is actually data there. You can verify the existence of data by checking for null geometries:

select * from "Edigeo"."GEOM" where geom_surf is NULL

This tip from the PostGIS website explains in a bit more detail and includes examples of other checks you can carry out.