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https://issues.apache.org/jira/browse/LUCENE-843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12506752
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Michael Busch commented on LUCENE-843:
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Hi Mike,

my first comment on this patch is: Impressive!

It's also quite overwhelming at the beginning, but I'm trying to dig into it. 
I'll probably have more questions, here's the first one:

Does DocumentsWriter also solve the problem DocumentWriter had before 
LUCENE-880? I believe the answer is yes. Even though you close the TokenStreams 
in the finally clause of invertField() like DocumentWriter did before 880 this 
is safe, because addPosition() serializes the term strings and payload bytes 
into the posting hash table right away. Is that right?

> improve how IndexWriter uses RAM to buffer added documents
> ----------------------------------------------------------
>
>                 Key: LUCENE-843
>                 URL: https://issues.apache.org/jira/browse/LUCENE-843
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.2
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>         Attachments: index.presharedstores.cfs.zip, 
> index.presharedstores.nocfs.zip, LUCENE-843.patch, LUCENE-843.take2.patch, 
> LUCENE-843.take3.patch, LUCENE-843.take4.patch, LUCENE-843.take5.patch, 
> LUCENE-843.take6.patch, LUCENE-843.take7.patch, LUCENE-843.take8.patch, 
> LUCENE-843.take9.patch
>
>
> I'm working on a new class (MultiDocumentWriter) that writes more than
> one document directly into a single Lucene segment, more efficiently
> than the current approach.
> This only affects the creation of an initial segment from added
> documents.  I haven't changed anything after that, eg how segments are
> merged.
> The basic ideas are:
>   * Write stored fields and term vectors directly to disk (don't
>     use up RAM for these).
>   * Gather posting lists & term infos in RAM, but periodically do
>     in-RAM merges.  Once RAM is full, flush buffers to disk (and
>     merge them later when it's time to make a real segment).
>   * Recycle objects/buffers to reduce time/stress in GC.
>   * Other various optimizations.
> Some of these changes are similar to how KinoSearch builds a segment.
> But, I haven't made any changes to Lucene's file format nor added
> requirements for a global fields schema.
> So far the only externally visible change is a new method
> "setRAMBufferSize" in IndexWriter (and setMaxBufferedDocs is
> deprecated) so that it flushes according to RAM usage and not a fixed
> number documents added.

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