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https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12981380#action_12981380
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Michael Busch commented on LUCENE-2324:
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bq. Really? That makes synchronized seem simpler?
Well look at ThreadAffinityDocumentsWriterThreadPool. There I'm able to use
things like tryLock() and getQueueLength().
Also DocumentsWriterPerThreadPool has a getAndLock() method, that can be used
by DW for addDocument(), whereas DW.flush(), which needs to iterate the DWPTs,
can lock the individual DWPTs directly. I think it's simpler, but I'm open to
other suggestions of course :)
bq. What about the memory used, eg, the non-use of byte[] recycling? I guess
it'll be cleared on flush.
Yeah, sure. That is independent on whether they're all created upfront or not.
But yeah, after flush or abort we need to clear the DWPT's state to make sure
they're not consuming unused RAM (as you described in your earlier comment).
> 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, 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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