Message-ID: <0aea4ab65af243d2a326ee92df68bd9309c64433.camel@cybertec.at>
Subject: Re: Foreign tables - oracle_fdw
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Edwin UY <edwin.uy@gmail.com>, pgsql-admin@lists.postgresql.org
Date: Sun, 05 May 2024 05:58:23 +0200
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On Sun, 2024-05-05 at 15:07 +1200, Edwin UY wrote:
> I followed this link for using oracle_fdw to access Oracle from PostgreSQ=
L.
> Oracle is ON-PREM and PostgreSQL is Aurora-PostgreSQL-RDS-Version 15.
>=20
> As administrator:
>=20
> CREATE EXTENSION oracle_fdw;
> CREATE SERVER oradb FOREIGN DATA WRAPPER oracle_fdw OPTIONS (dbserver '//=
endpoint:port/DB_name');
> GRANT USAGE ON FOREIGN SERVER oradb TO user1;
> As user1
>=20
> CREATE USER MAPPING FOR user1 SERVER oradb OPTIONS (user 'oracleuser', pa=
ssword 'mypassword');
> CREATE FOREIGN TABLE mytab (a int) SERVER oradb OPTIONS (table 'MYTABLE')=
;
> SELECT * FROM mytab;
> The SELECT gives ERROR: =C2=A0permission denied for schema public
> I have to do GRANT ALL ON SCHEMA public TO user1, this resolves the permi=
ssion denied error.
>=20
> Ideally, I don't really want each user to be doing the create user mappin=
g and create foreign table.
>=20
> Is it possible that as schema owner of either schema1 or schema2, i.e. ad=
ministrator,
> I create the user mapping and the foreign tables and then grant access to
> user1 to user5 and schema2/schema1?
> I can't find any reference/doc/example on whether this is possible or not=
.
>=20
> I also don't have the password of each user. Can I use set role user1 to =
user5 to do
> the CREATE USER MAPPING and CREATE FOREIGN TABLE.
>=20
> In summary, I am wanting to do the CREATE USER MAPPING and CREATE FOREIGN=
 TABLE once
> only in either SCHEMA1 and SCHEMA2 and grant any role/user to be able to =
access these
> foreign tables, mainly just a select.

The foreign table needs to be created only once, but you must give all user=
s privileges
to access the schema (USAGE) and the foreign table (SELECT, ...).

You will need a shared schema that all users can use and place the foreign =
table there.
That schema need not be "public".

If you don't want to create a user mapping for each user, you can also crea=
te a user
mapping for PUBLIC.  Sich a user mapping will work for all authenticated us=
ers, and they
will all use the same Oracle user to connect to the remote database.
If you want your users to use different Oracle users, you need to create a =
user mapping
for each individual user.

Yours,
Laurenz Albe