PostgreSQL - Using contrib

Im using intarray contrib
pgadmin III:
select ARRAY[1,2,3,4] - ARRAY[1,2,3]
result:
'{4}'

heidiSQL:
select ARRAY[1,2,3,4] - ARRAY[1,2,3]
ERROR: operator does not exist: integer[] - integer[]

PostgreSQL 9.3.4 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4), 64-bit

Tks

I get the same error from the PG server.

What exactly is "intarray contrib"?

execute "create extension intarray"

http://www.postgresql.org/docs/9.3/static/intarray.html

Tks