Sqoop uses MapReduce + DBInputFormat to read the contents of a table into HDFS. On many databases, this implementation is O(N^2) in the number of rows. Also, the use of multiple mappers has low value in terms of throughput, because the database itself is inherently singlethreaded. While DBInputFormat/JDBC provides a useful fallback mechanism for importing from databases, db-specific dump utilities will nearly always provide faster throughput, and should be selected when available. This patch allows users to use mysqldump to read from local mysql instances instead of the MapReduce-based input.
If you provide sqoop with arguments of the form " --connect jdbc:mysql://localhost/somedatabase --local", it will use the mysqldump fast path to perform the import.
This patch, naturally, requires that MySQL be installed on a machine to test it. Thus the test that this adds is called LocalMySQLTest (instead of the Hadoop-preferred file naming, TestLocalMySQL) so that Hudson doesn't automatically run it. You can run this test yourself by using "ant -Dtestcase=LocalMySQLTest test". See the notes in the javadoc for the LocalMySQLTest class in how to set up the MySQL test environment for this.