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https://issues.apache.org/jira/browse/LUCENE-2357?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand updated LUCENE-2357:
---------------------------------
Attachment: LUCENE-2357.patch
New Patch with two minor modifications:
- I replaced {{PackedInts.bitsRequired(numDocs)}} with
{{PackedInts.bitsRequired(Math.max(0, numDocs - 1))}} in {{buildDirectDocMap}}
since the highest doc id mapping is {{numDocs - 1}},
- {{Since DocMap.get}} now relies on {{liveDocs}} to return the doc mapping, I
added an assert in {{build}} to ensure that {{liveDocs}} is never null when
numDeletedDocs > 0.
> 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: 4.1
>
> 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.
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