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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, 10 Mar 2011 17:16:59 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13005172#comment-13005172
] 

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

bq. Is the max optimal DWPT size related to the size of the terms hash, or is it likely something
else?

Bigger really should be better I think.

Because 1) the RAM efficiency ought to scale up very well, as you see a given term in more
and more docs (hmm, though, maybe not, because from Zipf's law, half your terms will be singletons
no matter how many docs you index), and 2) less merging is required.

I'm not sure why in the past perf seemd to taper off and maybe get worst after RAM buffer
was over 256 MB... we should definitely re-test.

> 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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