[jira] Commented: (LUCENE-2324) Per thread DocumentsWriters that write their own private segments

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[jira] Commented: (LUCENE-2324) Per thread DocumentsWriters that write their own private segments

JIRA jira@apache.org

    [ https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12891663#action_12891663 ]

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

{quote}

bq. I think we don't need PerDocBuffer, either.  And this also simplifies RAM usage tracking!

The nice thing about that buffer is that on
non-aborting exceptions we can simply skip
the whole document, because nothing gets
written to the stores until finishDocument
is called.
{quote}

Well, though, if we did write it "live", since the doc is marked deleted, it would be "harmless" right?

Only difference is it took up some disk space (which should be minor given that it's not "normal" to have lots of docs hitting non-aborting exceptions).

Also... when the doc is large, the fact that we double buffer (write first to RAMFile then to the store) can be costly.  Ie we consume 1X the stored-field size in transient RAM, vs writing directly to disk, I think?

> 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.patch, 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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