At some deployment scenarios, one may have to access Oracle tables transparently using PostgreSQL functions, without installing other language specific libraries.

There is a caveat for this version:

• Each query will load data from remote Oracle server to the local PostgreSQL shadow table.
• You can execute remotely on Oracle backend using remote_select as described here.

Installation

You will need the alien package to convert rpm files to deb files.

You will need to have an Oracle account to download the Oracle Instant Client Basic and Oracle Instant Client Devel rpm files suitable for your Oracle backend version from the vendor site.

At this example, we will use

oracle-instantclient-basic-10.2.0.3-1.i386.rpm

oracle-instantclient-devel-10.2.0.3-1.i386.rpm

Convert *.rpm to *.deb

The alien package makes a brute conversion from rpm to deb, without careful checks. You must to test the results on a disposable laboratory machine before deploying at a valuable server.

debian:~# alien --to-deb oracle-instantclient-basic-10.2.0.3-1.i386.rpm 
debian:~# dpkg --install oracle-instantclient-basic_10.2.0.3-2_i386.deb
debian:~# alien --to-deb oracle-instantclient-devel_10.2.0.3-2_i386.rpm
debian:~# dpkg --install oracle-instantclient-devel_10.2.0.3-2_i386.deb

Install dbi-link and dependencies

The libaio1 is needed by the oracle programs.

debian:~# apt-get update
debian:~# apt-get install libdbd-oracle-perl dbi-link libaio1

Configure Oracle Instant Client Basic

Prepare the tnsnames.ora

debian:~# mkdir -p /usr/lib/oracle/10.2.0.3/client/network/admin/
debian:~# nano /usr/lib/oracle/10.2.0.3/client/network/admin/tnsnames.ora
</pre>

/usr/lib/oracle/10.2.0.3/client/network/admin/tnsnames.ora

A very simple example below, adapt it to your Oracle available database service.

your_symbolic_service_name =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP) (HOST = your_oracle_server_address)(PORT = 1521))
    )
    (CONNECT_DATA = (SID = your_available_oracle_sid))
  )

/usr/lib/oracle/10.2.0.3/client/network/admin/sqlnet.ora

We will not use sqlnet.ora at this example. Please read the useful links section at the end of article.

/etc/ld.so.conf.d/oracle.conf

/usr/lib/oracle/10.2.0.3/client/lib

debian:~# nano /etc/ld.so.conf.d/oracle.conf
debian:~# ldconfig

Configuring DBI-Link for PostgreSQL access Oracle tables

The step for creating the accessor_functions may be lenghty as it downloads all tables informations from the Oracle backend.

Your local schema MUST NOT EXISTS before creating the accessor functions. Read the dbi-link debian package documentation on your disk.

There are paremeters you must edit to your needs, like the oracle server port, and we use an example query.

Notably, the connection string:

'dbi:Oracle:host=your_oracle_server_address;sid=your_available_oracle_sid;port=1521',

could be something like:

'dbi:Oracle:user=your_available_oracle_username;host=your_oracle_server_address;sid=your_available_oracle_sid;port=1521',

or even could be:

'dbi:Oracle:database=your_oracle_available_database;host=your_oracle_server_address;sid=your_available_oracle_sid;port=1521',

It depends on your user access permissions and Oracle configuration files. Be careful with the syntax.

When it enters psql the first time, one must update the pg_settings for the dbi-link too. The sql is at the Debian dbi-link package documentation.

debian:~# su postgres
postgres@debian:/root$ createdb teste
postgres@debian:/root$ createlang plperlu teste
postgres@debian:/root$ psql -d teste -f /usr/share/dbi-link/dbi_link.sql 
postgres@debian:/root$ psql teste
Bem vindo ao psql 8.3.14, o terminal iterativo do PostgreSQL.

Digite:  \copyright para mostrar termos de distribuição
         \h para ajuda com comandos SQL
         \? para ajuda com comandos do psql
         \g ou terminar com ponto-e-vírgula para executar a consulta
         \q para sair

teste=# UPDATE                     
    pg_catalog.pg_settings
SET
    setting =
        CASE WHEN 'dbi_link' = ANY(string_to_array(setting, ','))
        THEN setting
        ELSE 'dbi_link,' || setting
        END
WHERE
    name = 'search_path'
;

teste=# SELECT make_accessor_functions(
    'dbi:Oracle:host=your_oracle_server_address;sid=your_available_oracle_sid;port=1521',
    'your_available_oracle_username',
    'your_available_oracle_password',
    '---                                                         
AutoCommit: 1
RaiseError: 1
',         
    NULL,
    NULL,               
    NULL,
    'your_local_schema'
);

teste=# \d
teste=# select count(*) from your_local_schema."VW_SISCOR_02";
teste=# select  count(*) from your_local_schema."VW_LOTACAO";
teste=# select  count(*) from your_local_schema."VW_LOTACAO" where "UF" = 'RS';
teste=# \q
postgres@debian:/root$ exit
exit
debian:~# 

Useful Links

http://keniamilene.wordpress.com/2008/05/29/instalando-e-implementando-dbi-link-no-postgresql/

http://thomas.eibner.dk/oracle/dbi/

https://github.com/davidfetter/DBI-Link

http://pgfoundry.org/forum/forum.php?set=custom&forum_id=161&style=nested&max_rows=25&submit=Change+View

http://www.mail-archive.com/dbi-link-general@pgfoundry.org/msg00055.html

http://pgfoundry.org/forum/forum.php?thread_id=2339&forum_id=162

http://pgfoundry.org/forum/forum.php?forum_id=161

http://alexzeng.wordpress.com/2010/10/16/perl-dbi-connect-oracle-example/

http://www.orafaq.com/wiki/Perl

http://www.easysoft.com/applications/oracle/database-gateway-dg4odbc.html

http://www.easysoft.com/developer/languages/perl/dbd_odbc_tutorial_part_1.html

http://search.cpan.org/~pythian/DBD-Oracle-1.27/Oracle.pm

http://pgfoundry.org/pipermail/dbi-link-general/2006-October/000051.html

http://www.mail-archive.com/pgbr-geral@listas.postgresql.org.br/msg18322.html

http://www.pgcon.org/2008/schedule/events/88.en.html

http://www.pythian.com/news/8369/dbdoracle-1-24-released/

http://www.php-pt.com/index.php?option=com_joomlaboard&Itemid=27&func=view&view=threaded&id=3652&catid=4

http://comments.gmane.org/gmane.comp.db.postgresql.dbi-link/65

http://www.eggheadcafe.com/software/aspnet/35697949/postgresql-to-oracle.aspx

http://www.devmedia.com.br/post-1945-Criando-Visoes--Views-no-Oracle.html

http://packages.debian.org/lenny/libdbd-oracle-perl

http://packages.debian.org/lenny/dbi-link

http://postgresql.1045698.n5.nabble.com/Visao-do-oracle-no-postgresql-td2049948.html

http://pgfoundry.org/docman/view.php/1000045/48/IMPLEMENTATION.txt

Oracle access files tnsnames.ora , sqlnet.ora

http://download.oracle.com/docs/cd/B28359_01/network.111/b28317/sqlnet.htm

http://profissionaloracle.com.br/blogs/rodrigoalmeida/tag/sqlnetora/

http://www.orafaq.com/wiki/Sqlnet.ora#Sample_sqlnet.ora_files

http://support.verio.com/documents/view_article.cfm?doc_id=1495

http://profissionaloracle.com.br/blogs/rodrigoalmeida/tag/tnsnamesora/

http://www.techforce.com.br/news/linux_blog/oracle_10g_r2_in_debian_domu_into_debian_dom0

http://www.techforce.com.br/news/linux_blog/instalar_oracle_client_no_debian_e_ubuntu

http://canonical.wordpress.com/2009/01/04/simple-oracle-instant-client-installation-on-debian-linux/

http://www.oracle.com/technetwork/topics/linuxsoft-082809.html

http://www.oracle.com/technetwork/database/10201linuxsoft-097986.html

Running Perl from PHP

http://pecl.php.net/package/perl

http://devzone.zend.com/article/1712

http://www.linuxjournal.com/article/9282?page=0,0

http://www.codingforums.com/showthread.php?t=189538

http://bytes.com/topic/php/answers/836-how-call-perl-function-php

http://theos.in/perl/how-to-call-perl-or-php-script-from-html-file/