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From "Michael Busch (JIRA)" <>
Subject [jira] Commented: (LUCENE-2312) Search on IndexWriter's RAM Buffer
Date Sun, 14 Mar 2010 23:27:27 GMT


Michael Busch commented on LUCENE-2312:

Michael are you also going to [first] tackle truly separating the RAM segments? I think we
need this first ...

Yeah I agree.  I started working on a patch for separating the doc writers already.

I also have a separate indexing chain prototype working with searchable RAM buffer (single-threaded),
but slightly different postinglist format (some docs nowadays only have 140 characters ;)
). It seems really fast.  I spent a long time thinking about lock-free algorithms and data
structures, so indexing performance should be completely independent of the search load (in
theory).  I need to think a bit more about how to make it work with "normal" documents and
Lucene's current in-memory format.

> Search on IndexWriter's RAM Buffer
> ----------------------------------
>                 Key: LUCENE-2312
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Search
>    Affects Versions: 3.0.1
>            Reporter: Jason Rutherglen
>            Assignee: Michael Busch
>             Fix For: 3.1
> In order to offer user's near realtime search, without incurring
> an indexing performance penalty, we can implement search on
> IndexWriter's RAM buffer. This is the buffer that is filled in
> RAM as documents are indexed. Currently the RAM buffer is
> flushed to the underlying directory (usually disk) before being
> made searchable. 
> Todays Lucene based NRT systems must incur the cost of merging
> segments, which can slow indexing. 
> Michael Busch has good suggestions regarding how to handle deletes using max doc ids.
> The area that isn't fully fleshed out is the terms dictionary,
> which needs to be sorted prior to queries executing. Currently
> IW implements a specialized hash table. Michael B has a
> suggestion here: 

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