[Feature Request] JDBCTap that can run in Local mode

[amatsukawa]

Currently JDBCTap is defined as Tap<JobConf, RecordReader, OutputCollector> which is incompatible with Cascading's local mode, which uses java.util.Properties rather than org.apache.hadoop.mapred.JobConf.

It would be useful to run cascading-jdbc in local mode, for a number of reasons, such as

1. Testing. For example we would like to unit test our JDBC integration in Scalding, but not able to execute in local mode makes it impractical.
2. Small jobs. During development, or production, it may be useful to execute a job in local mode that can nevertheless connect to DBs.

[cwensel]

the JDBCTap for Hadoop is coupled to Hadoop MapReduce and HDFS and the Cascading Hadoop planner.

A JDBCTap for Cascading local mode will need to be a new implementation, though there can be a common base class for the Tap and Scheme that has no platform dependent dependencies.

as Cascading starts to adopt new platforms (Tez, etc), it makes little sense to have a Tap with ties to all of them, so continuing a precedent (like TextDelimited) that shares common functionality but isolates platform dependencies is the correct approach.

that said, @fs111 and I have no plans to do this at the moment. But will leave this open for now in case a third-party wants to take a shot at it.