newbie needs help with postgres internal tables

Hi, everybody.

This is my first post on this list and I hope It's the good place for my
question.

I'm developping an Opensource projetc which aims to be a GTK
frontend for Postgresql first ( and other DB later ), whose name will be
GPF ( GPF is not a Postgresql Frontend ).

So I need to use mysef tables like pg_class, pg_attribute, pgdatabase.

By now, I need two things :

1- Find all the fields that belongs to a particular table.

It was difficult to find the good fiels but I found this query, which seems
to be good for me.

select attname
from pg_attribute a
where a.attnum>0
and
a.attrelid= ( select oid
from pg_class c
where c.relname='gpf_db') ;

( 'gpf_db' is the name of the database I'm searching all the fattributes )
( Is ther a better way to do this )

does a documentation exists concerning postgres internals, which I
havren't found, and which would say something like
"the relation between pg_class and pg_attribute is the field
oid in in pg_class which is the same as the field attrelid in pg_attribute"
"attnum in pg_attribute is >0 for 'user' fields and <0 for internal fields"
. . .

( In fact I would need a map of all the relations between all the internal
tables in postgres ;- ))

1- Find all the tables that belong to a particular database.

I have not been able to find an ID in pg_table or pg_class which
would help me finding all the tables that belong to a particular database.
the only thing I could do is selecting on the field tableowner
BUT
a user can have more than one database and all the tables of all the
databases owned by this user will have the same tableowner.

PS : sorry if my english is not always the best, I'm French ;-)

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