[HBASE-6072] Make TableRecordReaderImpl more easily extended

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Not A Problem
• Component/s: mapreduce
• Assignee: Unassigned
• Reporter: Dave Latham
• Created: 23/May/12 16:15
• Updated: 13/Jun/22 16:42
• Resolved: 11/Apr/15 01:31

Description

We have a MR job that is very memory bound. It reads a potentially large row from hbase, then deserializes it into an (even larger) object representation, then does a fair amount of computation requiring memory. After converting the Result into our object representation we want to free the memory holding the Result to be available for the actual computation of output values.

Currently we have our own custom modified copy of TableRecordReaderImpl to be able to set the Result value to null after reading it, but it's almost entirely a duplicate of hbase's TableRecordReaderImpl so we have to manually keep it up to date with changes to the hbase version. If the value field of TableRecordReaderImpl were protected instead of private we could use a very simple subclass instead.

Are there any philosophical guidelines about what parts of HBase should or should not be easily extensible?