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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 Mon, 15 Mar 2010 17:59:28 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12845428#action_12845428
] 

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

{quote}
bq. Seems ilke it's 8 bytes

Object header is two words, so that's 16bytes for 64bit arch. (probably 12 for 64bit+CompressedOops?)
{quote}

Right, and the pointer'd also be 8 bytes (but compact int stays at 4
bytes) so net/net on 64bit JRE savings would be 16-20 bytes per term.

Another thing we could do if we cutover to parallel arrays is to
switch to packed ints.  Many of these fields are horribly wasteful as
ints, eg docFreq or lastPosition.


> 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
>
>
> 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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