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Posts Tagged ‘postgresql’

Connecting Oracle database from PostgreSQL using Public DB Links.

Posted by FatDBA on August 31, 2020

Hi Guys,

This post is in continuation of my last post where I showed how to connect to Oracle database from an PostgreSQL instance. Last post was all about accessing Oracle database using Foreign data wrappers. This post is about accessing/querying Oracle database from PostgreSQL using DB Links.

Software Used:
Oracle Instant Clients (Need both BASIC and DEVEL packages)
Link: https://www.oracle.com/database/technologies/instant-client/linux-x86-64-downloads.html

For this method too, you have to install Oracle instant basic and devel packages.


[enterprisedb@fatdba ~]$ sudo rpm -Uvh oracle-instantclient12.2-basic-12.2.0.1.0-1.x86_64.rpm
[sudo] password for enterprisedb:
Preparing...                ########################################### [100%]
   1:oracle-instantclient12.########################################### [100%]
[enterprisedb@fatdba ~]$
[enterprisedb@fatdba ~]$ sudo rpm -Uvh oracle-instantclient12.2-devel-12.2.0.1.0-1.x86_64.rpm
Preparing...                ########################################### [100%]
   1:oracle-instantclient12.########################################### [100%]
[enterprisedb@fatdba ~]$

[enterprisedb@fatdba ~]$
[enterprisedb@fatdba ~]$ ls -ll /usr/lib/oracle/12.2/client64/lib
total 216568
lrwxrwxrwx. 1 root root        21 Aug 27 22:59 libclntshcore.so -> libclntshcore.so.12.1
-rw-rwxr--. 1 root root   8033199 Jan 26  2017 libclntshcore.so.12.1
lrwxrwxrwx. 1 root root        17 Aug 27 22:59 libclntsh.so -> libclntsh.so.12.1
-rw-rwxr--. 1 root root  71638263 Jan 26  2017 libclntsh.so.12.1
-rw-rwxr--. 1 root root   2981501 Jan 26  2017 libipc1.so
-rw-rwxr--. 1 root root    539065 Jan 26  2017 libmql1.so
-rw-rwxr--. 1 root root   6568149 Jan 26  2017 libnnz12.so
lrwxrwxrwx. 1 root root        15 Aug 27 22:59 libocci.so -> libocci.so.12.1
-rw-rwxr--. 1 root root   2218687 Jan 26  2017 libocci.so.12.1
-rw-rwxr--. 1 root root 124771800 Jan 26  2017 libociei.so
-rw-rwxr--. 1 root root    158543 Jan 26  2017 libocijdbc12.so
-rw-rwxr--. 1 root root    380996 Jan 26  2017 libons.so
-rw-rwxr--. 1 root root    116563 Jan 26  2017 liboramysql12.so
-rw-r--r--. 1 root root   3984814 Jan 26  2017 ojdbc8.jar
-rw-rwxr--. 1 root root    312974 Jan 26  2017 ottclasses.zip
-rw-r--r--. 1 root root     37494 Jan 26  2017 xstreams.jar
[enterprisedb@fatdba ~]$
 


Cool, let’s connect with the PostgreSQL instance and create the DBLink. To create that you need Oracle username and its password which you want to connect and its IP address along with SID or database name, and you are done. And yes, don’t forget to set the LD_LIBRARY_PATH to the location of your Oracle instant client.


[enterprisedb@fatdba ~]$ export LD_LIBRARY_PATH=/usr/lib/oracle/12.2/client64/lib
[enterprisedb@fatdba ~]$
[enterprisedb@fatdba ~]$ psql -d enterprisedb -U enterprisedb
psql.bin (10.12.20)
Type "help" for help.
enterprisedb=#
enterprisedb=#
enterprisedb=# select version();
                                                    version
---------------------------------------------------------------------------------------------------------------
 EnterpriseDB 10.12.20 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23), 64-bit
(1 row)

enterprisedb=#
enterprisedb=# CREATE DATABASE LINK dixdroid CONNECT TO migr IDENTIFIED BY 'oracle90' USING oci '//10.0.0.130/fatdb';
CREATE DATABASE LINK
enterprisedb=#
 


Great, now time to test. Lets do a query on Oracle’s table from Postgresql instance using DB Link named ‘dixdroid’ which we have created earlier.



enterprisedb=# select * from migr.bigtab1@dixdroid;
  id  |    created_date    | lookup_id |            data
------+--------------------+-----------+----------------------------
  320 | 19-MAY-19 02:10:38 |         1 | This is some data for 320
  321 | 19-MAY-18 02:10:38 |         2 | This is some data for 321
  322 | 19-MAY-19 02:10:38 |         1 | This is some data for 322
  323 | 19-MAY-20 02:10:38 |         3 | This is some data for 323
  324 | 19-MAY-18 02:10:38 |         2 | This is some data for 324
  325 | 19-MAY-20 02:10:38 |         3 | This is some data for 325
  326 | 19-MAY-19 02:10:38 |         1 | This is some data for 326
  327 | 19-MAY-18 02:10:38 |         2 | This is some data for 327
  328 | 19-MAY-19 02:10:38 |         1 | This is some data for 328
  329 | 19-MAY-20 02:10:38 |         3 | This is some data for 329
  330 | 19-MAY-18 02:10:38 |         2 | This is some data for 330
  331 | 19-MAY-20 02:10:38 |         3 | This is some data for 331
 

Great, it worked like a charm!

Hope It Helps
Prashant Dixit

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