Details
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New Feature
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Status: Closed
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Major
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Resolution: Fixed
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Reviewed
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New contribution Sqoop is a JDBC-based database import tool for Hadoop.
Description
Overview:
Sqoop is a tool designed to help users import existing relational databases into their Hadoop clusters. Sqoop uses JDBC to connect to a database, examine the schema for tables, and auto-generate the necessary classes to import data into HDFS. It then instantiates a MapReduce job to read the table from the database via the DBInputFormat (JDBC-based InputFormat). The table is read into a set of files loaded into HDFS. Both SequenceFile and text-based targets are supported.
Longer term, Sqoop will support automatic connectivity to Hive, with the ability to load data files directly into the Hive warehouse directory, and also to inject the appropriate table definition into the metastore.
Some more specifics:
Sqoop is a program implemented as a contrib module. Its frontend is invoked through "bin/hadoop jar sqoop.jar ..." and allows you to connect to arbitrary JDBC databases and extract their tables into files in HDFS. The underlying implementation utilizes the JDBC interface of HADOOP-2536 (DBInputFormat). The DBWritable implementation needed to extract a table is generated by this tool, based on the types of the columns seen in the table. Sqoop uses JDBC to examine the table specification and translate this to the appropriate Java types.
The generated classes are provided as .java files for the user to reuse. They are also compiled into a jar and used to run a MapReduce task to perform the data import. This either results in text files or SequenceFiles in HDFS. In the latter case, these Java classes are embedded into the SequenceFiles as well.
The program will extract a specific table from a database, or optionally, all tables. For a table, it can read all columns, or just a subset. Since HADOOP-2536 requires that a sorting key be specified for the import task, Sqoop will auto-detect the presence of a primary key on a table and automatically use it as the sort order; the user can also manually specify a sorting column.
Example invocations:
To import an entire database:
hadoop jar sqoop.jar org.apache.hadoop.sqoop.Sqoop --connect jdbc:mysql://db.example.com/company --all-tables
(Requires that all tables have primary keys)
To select a single table:
hadoop jar sqoop.jar org.apache.hadoop.sqoop.Sqoop --connect jdbc:mysql://db.example.com/company --table employees
To select a subset of columns from a table:
hadoop jar sqoop.jar org.apache.hadoop.sqoop.Sqoop --connect jdbc:mysql://db.example.com/company --table employees --columns "employee_id,first_name,last_name,salary,start_date"
To explicitly set the sort column, import format, and import destination (the table will go to /shared/imported_databases/employees):
hadoop jar sqoop.jar org.apache.hadoop.sqoop.Sqoop --connect jdbc:mysql://db.example.com/company --table employees --order-by employee_id --warehouse-dir /shared/imported_databases --as-sequencefile
Sqoop will automatically select the correct JDBC driver class name for HSQLdb and MySQL; this can also be explicitly set, e.g.:
hadoop jar sqoop.jar org.apache.hadoop.sqoop.Sqoop --connect jdbc:postgresql://db.example.com/company --driver org.postgresql.Driver --all-tables
Testing has been conducted with HSQLDB and MySQL. A set of unit tests covers a great deal of Sqoop's functionality, and this tool has been used in practice at Cloudera and with a few other early test users on "real" databases.
A readme file is included in the patch which contains documentation on how to use the tool.
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