Question

Consider I have a user-defined type as follows:

CREATE TYPE mytype AS
 (myvar character(1),
  myvar2 bit(10));

Can I use any of Postgres’s information tables in order to get the attribute information for this type:

I.e. given “mytype”, the information I want is:

• myvar : character(1)
• myvar2 : bit(10)

Answer 1

Yes, the pg_type table will have the typrelid column populated. This is an OID key for the pg_class table, which then is used in pg_attribute tables, just as with tables, views, indices etc. So sth like:

select attname, format_type(atttypid, atttypmod)
from pg_type
     join pg_class on pg_class.oid = pg_type.typrelid
     join pg_attribute on pg_attribute.attrelid = pg_class.oid
where typname = 'mytype'
order by attnum