During a restore operation, or in general when a table is created, you can see warning messages indicating that a column has unknown datatype. Below is an example for the warning message seen.
gpadmin=# create table dummy as select '1' as a, 'd'::text as d distributed by (d); WARNING: column "a" has type "unknown" DETAIL: Proceeding with relation creation anyway. gpadmin=# \d dummy Table "public.test1" Column | Type | Modifiers --------+---------+----------- a | unknown | d | text | Distributed by: (d)
In Pivotal Greenplum, which is based out of postgres, unknown column type is allowed. However, you will not be able to insert values other than character / varchar datatype. So, be careful while creating views or tables and define proper data type for a column. However, if in case some user has created tables / view with unknown data type, one can alter the column data type later as required to rectify it.
The warning message does not indicate a failure of gpdbrestore operation.
Below is an example to alter unknown datatype to integer.
gpadmin=# alter table dummy alter a type int ; ALTER TABLE gpadmin=# \d dummy Table "public.dummy" Column | Type | Modifiers --------+-------------------+----------- a | integer | d | text | Distributed by: (d)