[ http://issues.apache.org/jira/browse/HADOOP-54?page=comments#action_12422374 ] Doug Cutting commented on HADOOP-54: ------------------------------------
Re documentation: perhaps we should add file-format documentation to the javadoc as a part of this change. This could look something like Lucene's file-formats documentation (except simpler). That mixes a pseudo-formal BNF-like syntax with commentary: http://lucene.apache.org/java/docs/fileformats.html This should link to other javadoc to describe things like the zero-compressed int format. Eric's proposal looks good to me. I assume zero-compressed ints are meant most places he says 'delta compressed'. Is that right? It may make sense to delta compress the lists of key and value lengths, but it probably does not make sense to delta compress numPairs and the block lengths. > SequenceFile should compress blocks, not individual entries > ----------------------------------------------------------- > > Key: HADOOP-54 > URL: http://issues.apache.org/jira/browse/HADOOP-54 > Project: Hadoop > Issue Type: Improvement > Components: io > Affects Versions: 0.2.0 > Reporter: Doug Cutting > Assigned To: Arun C Murthy > Fix For: 0.5.0 > > > SequenceFile will optionally compress individual values. But both > compression and performance would be much better if sequences of keys and > values are compressed together. Sync marks should only be placed between > blocks. This will require some changes to MapFile too, so that all file > positions stored there are the positions of blocks, not entries within > blocks. Probably this can be accomplished by adding a > getBlockStartPosition() method to SequenceFile.Writer. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
