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https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12987827#action_12987827
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Jason Rutherglen commented on LUCENE-2324:
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I think we have a logical issue with updateDoc in that we're adding the delTerm
to *all* DWPTs, however we're flushing DWPTs un-synced. This means that a
delTerm would be applied to a segment prior to the DWPT with the new doc being
flushed. This can easily happen because even though getReader syncs on flush,
doFlush is not synced, meaning another concurrent flush may begin, merges may
be performed, all without the new doc being made available. The solution is
probably as simple as treating updateDoc deletes as *special* and storing them
in a Map<SegmentInfo/DWPT,<Term,Integer>> that belongs to the DWPT that
received the new doc (instead of adding the delTerm to each DWPT).
This updateDocDeletesMap would be flushed only when the DWPT [with the updated
doc] is flushed, and if a DWPT no longer exists, we can add the
delTerm to the last segment.
> Per thread DocumentsWriters that write their own private segments
> -----------------------------------------------------------------
>
> Key: LUCENE-2324
> URL: https://issues.apache.org/jira/browse/LUCENE-2324
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Reporter: Michael Busch
> Assignee: Michael Busch
> Priority: Minor
> Fix For: Realtime Branch
>
> Attachments: LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch,
> LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch,
> LUCENE-2324.patch, LUCENE-2324.patch, LUCENE-2324.patch, lucene-2324.patch,
> lucene-2324.patch, LUCENE-2324.patch, test.out, test.out, test.out, test.out
>
>
> See LUCENE-2293 for motivation and more details.
> I'm copying here Mike's summary he posted on 2293:
> Change the approach for how we buffer in RAM to a more isolated
> approach, whereby IW has N fully independent RAM segments
> in-process and when a doc needs to be indexed it's added to one of
> them. Each segment would also write its own doc stores and
> "normal" segment merging (not the inefficient merge we now do on
> flush) would merge them. This should be a good simplification in
> the chain (eg maybe we can remove the *PerThread classes). The
> segments can flush independently, letting us make much better
> concurrent use of IO & CPU.
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