Working with External Data on Oracle DB Docker
With multi-modal databases (such as Oracle and many more) you will typically work with data in different formats and for different purposes. One such data format is with data located external to the database. The data will exist in files on the operating systems on the DB server or on some connected storage device.
The following demonstrates how to move data to an Oracle Database Docker image and access this data using External Tables. (This based on an example from Oracle-base.com with a few additional commands).
For this example, I’ll be using an Oracle 21c Docker image setup previously. Similarly the same steps can be followed for the 18c XE Docker image, by changing the Contain Id from 21cFull to 18XE.
Step 1 – Connect to OS in the Docker Container & Create Directory
The first step involves connecting the the OS of the container. As the container is setup for default user ‘oracle’, that is who we will connect as, and it is this Linux user who owns all the Oracle installation and associated files and directories
docker exec -it 21cFull /bin/bash
When connected we are in the Home directory for the Oracle user.
The Home directory contains lots of directories which contain all the files necessary for running the Oracle Database.
Next we need to create a directory which will story the files.
As we are logged in as the oracle Linux user, we don’t have to make any permissions changes, as Oracle Database requires read and write access to this directory.
Step 3 – Upload files to Directory on Docker container
Open another terminal window on your computer (desktop/laptop). You should have two such terminal windows open. One you opened for Step 1 above, and this one. This will allow you to easily switch between files on your computer and the files in the Docker container.
Download the two Countries files, to your computer, which are listed on Oracle-base.com. Countries1.txt and Countries2.txt.
Now you need to upload those files to the Docker container.
docker cp Countries1.txt 21cFull:/opt/oracle/ext_data/Countries1.txt docker cp Countries2.txt 21cFull:/opt/oracle/ext_data/Countries2.txt
Step 4 – Connect to System (DBA) schema, Create User, Create Directory, Grant access to Directory
If you a new to the Database container, you don’t have any general users/schemas created. You should create one, as you shouldn’t use the System (or DBA) user for any development work. To create a new database user connect to System.
To use sqlplus command line tool you will need to install Oracle Instant Client and then SQLPlus (which is a separate download from the same directory for your OS)
To create a new user/schema in the database you can run the following (change the username and password to something more sensible).
create user brendan identified by BtPassword1
default tablespace users
temporary tablespace temp;
grant connect, resource to brendan;
alter user brendan quota unlimited on users;
Now create the Directory object in the database, which points to the directory on the Docker OS we created in the Step 1 above. Grant ‘brendan’ user/schema read and write access to this Directory
CREATE OR REPLACE DIRECTORY ext_tab_data AS '/opt/oracle/ext_data';
grant read, write on directory ext_tab_data to brendan;
Now, connect to the brendan user/schema.
Step 5 – Create external table and test
To connect to brendan user/schema, you can run the following if you are still using SQLPlus
SQL> connect brendan/BtPassword1@//localhost/XEPDB1
or if you exited it, just run this from the command line
Create the External Table (same code from oracle-base.com)
CREATE TABLE countries_ext ( country_code VARCHAR2(5), country_name VARCHAR2(50), country_language VARCHAR2(50) ) ORGANIZATION EXTERNAL ( TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_data ACCESS PARAMETERS ( RECORDS DELIMITED BY NEWLINE FIELDS TERMINATED BY ',' MISSING FIELD VALUES ARE NULL ( country_code CHAR(5), country_name CHAR(50), country_language CHAR(50) ) ) LOCATION ('Countries1.txt','Countries2.txt') ) PARALLEL 5 REJECT LIMIT UNLIMITED;
It should create for you. If not and you get an error then if will be down to a typo on directory name or the files are not in the directory or something like that.
We can now query the External Table as if it is a Table in the database.
SQL> set linesize 120 SQL> select * from countries_ext order by country_name; COUNT COUNTRY_NAME COUNTRY_LANGUAGE ----- ------------------------------------ ------------------------------ ENG England English FRA France French GER Germany German IRE Ireland English SCO Scotland English USA Unites States of America English WAL Wales Welsh 7 rows selected.