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https://issues.apache.org/jira/browse/LUCENE-1606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12780432#action_12780432
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Robert Muir commented on LUCENE-1606:
-------------------------------------
bq. So Robert - what do you think about paring down the automaton lib, and
shoving all this in core? I want it, I want, I want it
Mark, some notes on size. jarring up the full source code (no paring) is 81KB.
in practice, the jar file is larger because it contains some 'precompiled DFAs'
for certain things like Unicode blocks, XML types... are these really needed?
see here for a list of what I mean:
http://www.brics.dk/automaton/doc/dk/brics/automaton/Datatypes.html
I enabled these in the patch (they could be easily disabled): an example of how
they are used in a regexp is like this: <Arabic>* (match 0 or more arabic
characters)
if a user really wanted them, they can load them themselves, you can also
create custom ones and use a DataTypesAutomatonProvider to register them for
some name:
Example: your users want to be able to use <make> or <model> inside their
regexps, you can register <make> and <model> to match to some DFA you make
yourself.
its really a nice mechanism, but I don't think we need all the precompiled
ones?
> Automaton Query/Filter (scalable regex)
> ---------------------------------------
>
> Key: LUCENE-1606
> URL: https://issues.apache.org/jira/browse/LUCENE-1606
> Project: Lucene - Java
> Issue Type: New Feature
> Components: contrib/*
> Reporter: Robert Muir
> Assignee: Robert Muir
> Priority: Minor
> Fix For: 3.1
>
> Attachments: automaton.patch, automatonMultiQuery.patch,
> automatonmultiqueryfuzzy.patch, automatonMultiQuerySmart.patch,
> automatonWithWildCard.patch, automatonWithWildCard2.patch, LUCENE-1606.patch,
> LUCENE-1606.patch
>
>
> Attached is a patch for an AutomatonQuery/Filter (name can change if its not
> suitable).
> Whereas the out-of-box contrib RegexQuery is nice, I have some very large
> indexes (100M+ unique tokens) where queries are quite slow, 2 minutes, etc.
> Additionally all of the existing RegexQuery implementations in Lucene are
> really slow if there is no constant prefix. This implementation does not
> depend upon constant prefix, and runs the same query in 640ms.
> Some use cases I envision:
> 1. lexicography/etc on large text corpora
> 2. looking for things such as urls where the prefix is not constant (http://
> or ftp://)
> The Filter uses the BRICS package (http://www.brics.dk/automaton/) to convert
> regular expressions into a DFA. Then, the filter "enumerates" terms in a
> special way, by using the underlying state machine. Here is my short
> description from the comments:
> The algorithm here is pretty basic. Enumerate terms but instead of a
> binary accept/reject do:
>
> 1. Look at the portion that is OK (did not enter a reject state in the
> DFA)
> 2. Generate the next possible String and seek to that.
> the Query simply wraps the filter with ConstantScoreQuery.
> I did not include the automaton.jar inside the patch but it can be downloaded
> from http://www.brics.dk/automaton/ and is BSD-licensed.
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