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From: Wolf-D. Ihlenfeldt <wolf@molout.tutkie.tut.ac.jp>
To: postgres@postgres.Berkeley.EDU
Subject: How to retrieve owner of class
Date: Tue, 19 Jul 94 17:35:19 jst
Message-ID: <9407190835.AA03166@molout.tutkie.tut.ac.jp> (raw)



In Postgres4.2, the id of the owner of a class is stored as
pg_class.relowner as type 'oid'.
This entry refers to pg_user.usesysid, which is of type 'int2'.

Question 1: Why are the types different ?

I tried to retrieve class name and owner by
retrieve (c.relname, u.usename) from c in pg_class, u in pg_user
where u.usesysid = c.relowner

and I get
NOTICE:Jul 19 17:53:31:there is no operator = for types int2 and oid
NOTICE:Jul 19 17:53:31:You will either have to retype this query using an
NOTICE:Jul 19 17:53:31:explicit cast, or you will have to define the operator
WARN:Jul 19 17:53:31:= for int2 and oid using DEFINE OPERATOR

Casting does not work:

retrieve (c.relname, u.usename) from c in pg_class, u in pg_user
where u.usesysid = c.relowner::int2
NOTICE:Jul 19 17:54:16:there is no operator = for types int2 and oid
NOTICE:Jul 19 17:54:17:You will either have to retype this query using an
NOTICE:Jul 19 17:54:17:explicit cast, or you will have to define the operator
WARN:Jul 19 17:54:17:= for int2 and oid using DEFINE OPERATOR


I solved the problem by writing a private oid/int2 comparison 
function and introducing a '=' operator. However, I wonder if
this is really necessary.
Question 2: Is there another way to specify this query ?

Question 3: Looking at the built-in functions, I found names like
'oidint2' and functions for this type. However, these are NO 
oid/int2 functions, but seem to operate on an exotic oidint2 type.
What is this type being used for ?

WDI

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