Type conversion. What do I do with a PostgreSQL OID value in libpq in C?

Question

I\'m working with the PostgreSQL C API, libpq. I need to be able to convert the values in a PGresult* into their equivalent data types in Ruby. I\'m currently j

Answer 1

To get the type name from an OID, just cast it to regtype:

SELECT  700::oid::regtype -- real

To get the type of any columns (or variable in plpgsql), use pg_typeof():

SELECT  pg_typeof(1::real) -- real

Gives you an answer of type regtype which is displayed as text in psql or pgAdmin. You can cast it to text explicitly if needed:

SELECT  pg_typeof(1::real)::text -- real

There is also this "big list", vulgo catalog table pg_type, where types are registered. This can be big, have a peek:

SELECT * from pg_type LIMIT 10;

More info in the excellent manual.