Performance improvement for merging stored, compressed fields -------------------------------------------------------------
Key: LUCENE-629 URL: http://issues.apache.org/jira/browse/LUCENE-629 Project: Lucene - Java Issue Type: Improvement Components: Index Reporter: Michael Busch Priority: Minor Hello everyone, currently the merging of stored, compressed fields is not optimal for the following reason: every time a stored, compressed field is being merged, the FieldsReader uncompresses the data, hence the FieldsWriter has to compress it again when it writes the merged fields data (.fdt) file. The uncompress/compress step is unneccessary and slows down the merge performance significantly. This patch improves the merge performance by avoiding the uncompress/compress step. In the following I give an overview of the changes I made: * Added a new FieldSelectorResult constant named "LOAD_FOR_MERGE" to org.apache.lucene.document.FieldSelectorResult * SegmentMerger now uses an FieldSelector to get stored fields from the FieldsReader. This FieldSelector's accept() method returns the FieldSelectorResult "LOAD_FOR_MERGE" for every field. * Added a new inner class to FieldsReader named "FieldForMerge", which extends org.apache.lucene.document.AbstractField. This class holds the field properties and its data. If a field has the FieldSelectorResult "LOAD_FOR_MERGE", then the FieldsReader creates an instance of "FieldForMerge" and does not uncompress the field's data. * FieldsWriter checks if the field it is about to write is an instanceof FieldsReader.FieldForMerge. If true, then it does not compress the field data. To test the performance I index about 350,000 text files and store the raw text in a stored, compressed field in the lucene index. I use a merge factor of 10. The final index has a size of 366MB. After building the index, I optimize it to measure the pure merge performance. Here are the performance results: old version: * Time for Indexing: 36.7 minutes * Time for Optimizing: 4.6 minutes patched version: * Time for Indexing: 20.8 minutes * Time for Optimizing: 0.5 minutes The results show that the index build time improved by about 43%, and the optimizing step is more than 8x faster. A diff of the final indexes (old and patched version) shows, that they are identical. Furthermore, all junit testcases succeeded with the patched version. Regards, Michael Busch -- 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 --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]