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https://issues.apache.org/jira/browse/LUCENE-1606?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Robert Muir updated LUCENE-1606:
--------------------------------

    Attachment: LUCENE-1606-flex.patch

this is an update to improve performance for lots of seeking (wildcards like 
?????NN, crazy regular expressions, fuzzy)

* expose State.getNumber() as an expert method. this returns the consecutive 
integer of the state in the automaton.
* (re)use a bitset for tracking 'visited' instead of creating a hashset for 
each seek
* use an array indexed by state number for caching transitions, instead of a 
hashmap.


> 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: Search
>            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, 
> BenchWildcard.java, LUCENE-1606-flex.patch, LUCENE-1606-flex.patch, 
> LUCENE-1606-flex.patch, LUCENE-1606-flex.patch, LUCENE-1606-flex.patch, 
> LUCENE-1606-flex.patch, LUCENE-1606-flex.patch, LUCENE-1606-flex.patch, 
> LUCENE-1606-flex.patch, LUCENE-1606.patch, LUCENE-1606.patch, 
> LUCENE-1606.patch, LUCENE-1606.patch, LUCENE-1606.patch, LUCENE-1606.patch, 
> LUCENE-1606.patch, LUCENE-1606.patch, LUCENE-1606.patch, LUCENE-1606.patch, 
> LUCENE-1606.patch, LUCENE-1606.patch, LUCENE-1606.patch, LUCENE-1606.patch, 
> LUCENE-1606.patch, LUCENE-1606_nodep.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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