Sqoop import/export from/to Oracle

I love Sqoop! It's a fun tool to work with and it's very powerful. Importing and exporting data from/to Oracle by Sqoop is pretty straightforward. One crucial thing you need to remember when working with Sqoop and Oracle together, that is using all capital letters for Oracle table names. Otherwise, Sqoop will not recognize Oracle tables.

This is my database (Oracle) related information:

• URL: 10.0.0.24
• db_name (SID): test
• Schema: Employee_Reporting
• Username: username1
• Password: password1
• Tablename: employee ( I'm going to export this table to HDFS by Sqoop)

Import from Oracle to HDFS:

Let's go through this option file (option.par):

You can see most of the parameters are self-explanatory. Notice that I'm providing table name in all capital letters. How you want to see the imported columns in HDFS? For that, we need to use --fields-terminated-by parameter. Here I'm passing "\t" for that parameter, which means that the column or field for each rows will be tab delimited after import. Sqoop will generate a class(with a list of setter and getter) to invoke the employee object, the name of that class name is defined by --class-name parameter. So in this case, it will create a class named Employee.java inside com.example.reporting package. I'm using --verbose parameter to print out information while Sqoop is working. It's not mandatory and you can ignore it if you want. --split-by parameter represents the name of the column which I want to use for splitting the import data. Here, ID is the primary key of the table Employee. You can use any WHERE clause for your import, in that case you need to pass that with the --where parameter. For the above example, it will import all rows from the table Employee where ID is less than or equal to 100000 (e.g. importing 100000 rows). You need to mention a HDFS location which will be used as a destination directory for the imported data (--target-dir parameter). Remember one thing here is that the target directory should not be existing prior to run import command otherwise Sqoop will throw an error. The last parameter -m represents the number of map tasks to run in parallel for the entire import job.

Once you have your option file ready, you can execute the Sqoop import command as:

sqoop import --options-file option.par

Using option file is not mandatory, I'm just using it for my convenience. You can also pass each of the parameter from your console and execute the import job. Example:

Export from Hive to Oracle:

For export, I will be using some of the parameters which I used during import as they are common for both import and export job. Assume I processed(by MR jobs) the data generated by import job and inserted them into Hive tables. Now I want to export those Hive tables to Oracle. If you are familiar with Hive, you may know that Hive moves/copies data to its warehouse folder by default. I'm using Hortonworks's distribution and for my case Hive'e warehouse folder is located at: "/apps/hive/warehouse/emp_record". Here, emp_record is one of the Hive table I want to export from.

I have already created a matching table "Emp_Record" in my Oracle inside the same schema "Employee_Reporting". To export the Hive table, I'm executing the following command:

Notice that instead of using --target-dir, I'm using --export-dir, this is the location of the Hive table's warehouse folder and data will be exporting from there.

Now assume, inside the warehouse directory, I have a file 00000_1 (which contains the data of Hive table Emp_Record) and some of its lines are:

As you can see, each of columns/fields are tab delimited and each of the rows are separated by a new line. Again we see here that there is an entire row which contains null as their values (Ideally you might not have null values as you might want to filter those values from your M-R jobs). But say we have all kind of values, so we need to tell Sqoop how to treat each of those values. Because of that, I'm using --input-fields-terminated-by parameter to inform that the fields are tab delimited and --input-lines-terminated-by parameter to distinguish rows. Again from Sqoop side, there are two kinds of column - string column and non-string column. Sqoop needs to know what string value is interpreting a null value. Because of that I'm using --input-null-string and --input-null-non-string parameters for two column types and passing '\\N' as their value because for my case '\\N' is null.

Wrapping Up:

Sometimes you will face some issues during export when your Oracle table has a very tight constraint (e.g. not null, time-stamp, expecting value in specific format, etc). In that case, the best idea is to export the Hive table/HDFS data to a temporary Oracle table without any modification to make Sqoop happy :). And then write a SQL script to convert and filter those data to your expected values and load them into your main Oracle table.

The above two examples are just showing a very basic import and export Sqoop job. There are a lot of setting in Sqoop you can use. Once you are able to run export/import job successfully, I would recommend you to try the same job with different parameters and see how it goes. You can find all available options in the Sqoop user guide.

Note: For privacy purpose, I had to modify several lines on this post from my original post. So if you find something is not working or facing any issues, please do not hesitate to contact me.