Обсуждение: relation complex types

Hi,

I knew that we create an entry in pg_type for every table we create,
what i didn't know is that we actually create 2 entries.

for example CREATE TABLE foo (i int); will create types foo and _foo.
so, any reason to create 2 entries?
anyway, what really kept my attention is that CREATE SEQUENCE also
create an entry in pg_type. there is any reason for that?

--
Jaime Casanova         www.2ndQuadrant.com
Professional PostgreSQL: Soporte 24x7 y capacitación

Jaime Casanova wrote:
> I knew that we create an entry in pg_type for every table we create,
> what i didn't know is that we actually create 2 entries.
> 
> for example CREATE TABLE foo (i int); will create types foo and _foo.
> so, any reason to create 2 entries?

I don't know offhand; maybe its the corresponding row/tuple type and 
table/relation type?

> anyway, what really kept my attention is that CREATE SEQUENCE also
> create an entry in pg_type. there is any reason for that?

This I'm fairly sure, is due to a sequence generator being implemented as a 
table/relation-typed variable, so it has a corresponding type like the regular 
table/relation-typed variables in the database.

-- Darren Duncan

Darren Duncan <darren@darrenduncan.net> writes:
> Jaime Casanova wrote:
>> I knew that we create an entry in pg_type for every table we create,
>> what i didn't know is that we actually create 2 entries.
>> for example CREATE TABLE foo (i int); will create types foo and _foo.
>> so, any reason to create 2 entries?

> I don't know offhand; maybe its the corresponding row/tuple type and 
> table/relation type?

_foo is the array type foo[].  There was bellyaching about the extra
pg_type entries when we added support for arrays of complex types,
but it was decided that trying to suppress them for table rowtypes
would be too, um, complex.
        regards, tom lane