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https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12985148#action_12985148
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Jason Rutherglen commented on LUCENE-2324:
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bq. the cost of replaying the log, assuming the log is "smallish"
This is recording and replaying the doc-ids? How/when does a previous BV
become 'free' to be used by the next reader? What if they're open at the same
time? And if it's a previous previous reader that's been closed, won't that be
quite a few docids to save? Eg, a delete-by-query has removed thousands of
docs, I guess we'd use System.arraycopy then. The most usual case is
updateDocument with [N]RT, which'd generate few doc-ids.
bq. System.arraycopy, while fast, is still O(N)
Right, the larger segments will really adversely affect performance, as they do
today, however the indexing is so much slower with NRT + clone that it's not
noticeable.
bq. Using RT/NRT shouldn't slow down searching
Right! The cost needs to be in the indexing and/or reopen threads.
> 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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