Issue with Oracle Database Gateway for ODBC and Unicode

Hello,

I hope this is the right mailing list to post questions about pgsql odbc.
I am sorry if I made a mistake and it is not.

I have a Postgres database (9.1) and an Oracle database (10.2) whose
character set is utf8. I installed the 64-bit 9.1 unicode psqlodbc driver
along with the Oracle Database Gateway for ODBC (DG4ODBC), version 11.2
because I have the need to access data in the Postgres database from the
Oracle one.

It works fine, but we have noticed the following. When a query such as
this is issued in Oracle:

select * from "dps_user"@pg where "id" = '32422'

The where clause is dropped, and the query that reaches the Postgres
database is:

select * from "dps_user"

So the whole table data are brought from Postgres, and then the where
clause is applied in Oracle. This is pretty inefficient with big tables.

We have noticed that this only happens when the column in the where clause
is of type character varying, due to the fact that the Oracle Database
Gateway for ODBC returns all character varying columns in Postgres as type
NVARCHAR2. If we issue the query like this, then the where clause is
passed to Postgres:

select * from "dps_user"@pg where "id" = cast('32422' as nvarchar2(40))

This behavior does not happen when we used the psqlodbc ANSI driver, but
unfortunately the Unicode driver is a must because both databases contain
Japanese, Russian and Chinese characters. It does not happen either when
we access the Postgres database through the psqlodbc Unicode driver from,
for example, Microsoft Query, so it has something to do with the Oracle
Database Gateway.

However, I thought I would post my problem here, just in case you ran into
this problem or heard of someone who did. Having to use the cast as
nvarchar2 works, but it is very cumbersome. I wonder if there would be a
way to configure the psqlodbc driver so that a varchar2 column is returned
instead.

I am going to open a service request with Oracle to see if they can help
me on the gateway end.

Sorry again if this is not the right place for this question.

Thanks a lot,

Carlos