Hadoop ETL UDFs are the main way to transfer data between Exasol and Hadoop (HCatalog tables on HDFS). The SQL syntax for calling the UDFs is similar to that of Exasol's native IMPORT and EXPORT commands, but with added UDF paramters for specifying the various necessary and optional Hadoop properties.
A brief overview of features includes support for:
For a more detailed description of the features, please refer to the IMPORT and EXPORT sections below.
Before you can start using the Hadoop ETL UDFs, you have to deploy the UDFs in your Exasol database. Please follow the step-by-step deployment guide.
After deloying the UDFs, you can begin using them to easily transfer data to and from Hadoop.
The IMPORT UDFs load data into Exasol from Hadoop (HCatalog tables on HDFS). To import data, you just need to execute the SQL statement
IMPORT INTO ... FROM SCRIPT ETL.IMPORT_HCAT_TABLE WITH ... with the appropriate parameters. This calls the
ETL.IMPORT_HCAT_TABLE UDF, which was previously created during deployment.
For example, run the following statement to import data into an existing table.
CREATE TABLE sample_07 (code VARCHAR(1000), description VARCHAR (1000), total_emp INT, salary INT); IMPORT INTO sample_07 FROM SCRIPT ETL.IMPORT_HCAT_TABLE WITH HCAT_DB = 'default' HCAT_TABLE = 'sample_07' HCAT_ADDRESS = 'thrift://hive-metastore-host:9083' HCAT_USER = 'hive' HDFS_USER = 'hdfs';
Please see the IMPORT details for a full description.
The EXPORT UDFs load data from Exasol into Hadoop (HCatalog tables on HDFS). To export data, you just need to execute the SQL statement
EXPORT ... INTO SCRIPT ETL.EXPORT_HCAT_TABLE WITH ... with the appropriate parameters. This calls the
ETL.EXPORT_HCAT_TABLE UDF, which was previously created during deployment.
For example, run the following statement to export data from an existing table.
CREATE TABLE TABLE1 (COL1 SMALLINT, COL2 INT, COL3 VARCHAR(50)); EXPORT TABLE1 INTO SCRIPT ETL.EXPORT_HCAT_TABLE WITH HCAT_DB = 'default' HCAT_TABLE = 'test_table' HCAT_ADDRESS = 'thrift://hive-metastore-host:9083' HCAT_USER = 'hive' HDFS_USER = 'hdfs';
Please see the EXPORT details for a full description.
In case you cannot connect to certain parts of Hadoop it is a good idea to test the DNS hostname resolution and TCP/IP connectivity to all hosts and ports of Hadoop (HCatalog, HDFS, and Kerberos servers if used). For this you can use the python script in solution 325. Note that this script is designed for testing http connections, so you can ignore the http check failures.
Google DataProc Integration issues.