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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, 22 Apr 2010 17:09:59 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12859906#action_12859906
] 

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

{quote}
I'm not sure I understand how this would help for ParallelReader?
I think you can't use multi-threaded indexing even today, because you
have no control over the order in which the docs will make it into the
index.
{quote}

Well, to set up indexes for PR today, you have to run IndexWriter in a very degraded state
-- flush by doc count, use a single thread, turn off concurrent merging (use SMS), use LogDocMergePolicy.

{quote}
So having maxBufferedDocs per DWPT seems tempting to me. Then you know
that each written segment will have exactly a size of maxBufferedDocs,
so this is much more predictable. And if you index with a single 
thread only the behavior is identical to a "global" maxBufferedDocs
flush trigger.
{quote}
Yeah, maybe that'd be sufficient...?  It'd sort of "match" the current behaviour, in that
you get segments flushed to the index with that many docs.

> 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: 3.1
>
>         Attachments: lucene-2324.patch, LUCENE-2324.patch
>
>
> 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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