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From Michael McCandless <>
Subject Re: IndexWriter.getReader usage
Date Sun, 02 Aug 2009 18:44:11 GMT
It's likely the RAMDir approach will still be a performance win over
getReader, until LUCENE-1313 is in (which uses a RAMDir for the
small-enough newly flushed segments).  getReader() writes (but doesn't
sync) the new segment files to the Directory, and then opens a new
SegmentReader on those files, so it's paying the IO cost that the
RAMDir approach doesn't.  I'd love to see some real world results on
this, though; I think likely the gains are minor.

The biggest win for NRT was switching to per-segment Collector because
that meant we could re-use FieldCache entries for all segments that
hadn't changed.


On Sat, Aug 1, 2009 at 7:52 AM, Grant Ingersoll<> wrote:
> In many NRT cases, it seems the traditional approach has been to have two
> RAM directories and a write-through FS Directory (for example Zoie does
> this, and it has also been discussed a fair number of times on the various
> lists).  I'm wondering how the new IndexWriter.getReader stuff relates to
> that approach?  Is there even a need for the RAM dirs at this point?
> -Grant
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