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From "Michael McCandless (JIRA)" <>
Subject [jira] [Updated] (LUCENE-3830) MappingCharFilter could be improved by switching to an FST.
Date Thu, 03 May 2012 22:52:48 GMT


Michael McCandless updated LUCENE-3830:


New patch: I made a simple perf test (attached:, and found the FST was slower... I
fixed RollingCharBuffer to bulk read, and also pre-cache the FST arcs
in a HashMap (FST pre-caches only latin bytes), and now perf is a bit
faster.  I also switched to builder API (like SynFilter) so
the NormalizeCharMap instance is immutable.

I think it's ready!

We can separately improve the matching algo based on the 23 page

> MappingCharFilter could be improved by switching to an FST.
> -----------------------------------------------------------
>                 Key: LUCENE-3830
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Dawid Weiss
>            Assignee: Michael McCandless
>            Priority: Minor
>              Labels: gsoc2012, lucene-gsoc-12
>             Fix For: 4.0
>         Attachments: LUCENE-3830.patch, LUCENE-3830.patch,
> MappingCharFilter stores an overly complex tree-like structure for matching input patterns.
The input is a union of fixed strings mapped to a set of fixed strings; an fst matcher would
be ideal here and provide both memory and speed improvement I bet.

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