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Adrien Grand commented on LUCENE-2357: -------------------------------------- This is the theoretical improvement. However, in order not to slow merging down too much, I instantiate the {{PackedInts.Mutable}} that holds the doc map with {{acceptableOverheadRatio=PackedInts.FAST=50%}} (see LUCENE-4062), so the actual improvement might be a little worse than the theoretical improvement. If you are more interested in memory usage than in merge speed, you could still reach the theoretical improvement by replacing {{PackedInts.FAST}} with {{PackedInts.COMPACT}} in {{MergeState.DocMap.build}}. > Reduce transient RAM usage while merging by using packed ints array for docID > re-mapping > ---------------------------------------------------------------------------------------- > > Key: LUCENE-2357 > URL: https://issues.apache.org/jira/browse/LUCENE-2357 > Project: Lucene - Java > Issue Type: Improvement > Components: core/index > Reporter: Michael McCandless > Assignee: Michael McCandless > Priority: Minor > Fix For: 4.0 > > Attachments: LUCENE-2357.patch, LUCENE-2357.patch, LUCENE-2357.patch, > LUCENE-2357.patch, LUCENE-2357.patch > > > We allocate this int[] to remap docIDs due to compaction of deleted ones. > This uses alot of RAM for large segment merges, and can fail to allocate due > to fragmentation on 32 bit JREs. > Now that we have packed ints, a simple fix would be to use a packed int > array... and maybe instead of storing abs docID in the mapping, we could > store the number of del docs seen so far (so the remap would do a lookup then > a subtract). This may add some CPU cost to merging but should bring down > transient RAM usage quite a bit. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org