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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2324) Per thread DocumentsWriters that write their own private segments
Date Thu, 06 Jan 2011 00:32:49 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12978060#action_12978060
] 

Michael McCandless commented on LUCENE-2324:
--------------------------------------------

{queue}
Another model we could implement is a straight queuing. This'd give us total
ordering on all IW calls. Documents, deletes, and flushes would be queued up
and executed asynchronously. For example in today's DWPT code we will still
block document additions while flushing because we're tying a thread to a given
DWPT. If a thread's DWPT is flushing, wouldn't we want to simply assign the doc
add to a different non-flushing DWPT to gain full efficiency? This seems more
easily doable with a queuing model. If we want synchronous flushing then we'd
place a flush event in the queue and wait for it to complete executing. How
does this sound?
{queue}
I think we should have to add queueing to all incoming ops...

If a given DWPT is flushing then we pick another?  Ie the binding logic would naturally avoid
DWPTs that are not available -- either because another thread has it, or it's flushing.  But
it would prefer to use the same DWPT it used last time, if possible (affinity).

> 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.patch,
lucene-2324.patch, LUCENE-2324.patch, 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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