ADD: test of SchemaUtils.dumpColumns() and SchemaUtils.parseColumns()
MOD: JoinExecutor and MR.
The schema string includes the table name
ADD: TableDisplayer and TableGenerator
FIX: embed schema typo
FIX: typo generated by copy in RightMapper
MOD: LeftJoinMapper, add LOG
FIX: JoinReducer, setup the intersection key of left and join
MOD: throw exception when running is failed
FIX: uninitialized marker
ADD: Row#toString() for debug
ADD: Schema.columnNames, from cd to name
FIX: typo logic in natural join method
ADD: log file filters in TableDisplayer
FIX: JoinExecuter
must specify the input format: SequenceFileInputFormat
must specify the output format: SequenceFileOutputFormat
must run by ToolRunner.run() rather than Tool#run(), otherwise the getConf() would return null
must set key and value class, otherwise might be Text!