I apologize if this has been brought up before, but the Scan class acts
differently in regular client queries than in MapReduce jobs configured by
TableMapReduceUtil. I'm using the 0.20.0 release in standalone mode at the
moment for a proof of concept.
1. Startrow/Stoprow
Scan scan = new Scan( startRow, stopRow );
The "startrow", "stoprow" arguments don't seem to be honored in a MapReduce
jobs and it turns into a full tablescan.
2. Column selection
If you use this instance of Scan...
Scan scan = new Scan( startRow, stopRow );
... in regular client activity this instance will allow selection of attributes
in the Result. However, this same instance used in a MapReduce job will
produce the following exception:
Exception in thread "main" java.io.IOException: Expecting at least one column.
at
org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.getSplits(TableInputFormatBase.java:281)
The remedy is to call either "addColumn" or "addFamily" on the Scan instance as
appropriate, but it's a little odd that in one use case things will work and in
another it will exception.
Doug Meil
Director of Engineering
doug.m...@explorys.net
