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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1606) Automaton Query/Filter (scalable regex)
Date Sun, 22 Nov 2009 21:35:39 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12781223#action_12781223
] 

Robert Muir commented on LUCENE-1606:
-------------------------------------

bq. I thought you were about to open one!

I opened one for Automaton specifically, should i change it to be all MTQ?

bq. Actually... wouldn't we need to convert to int[] (for Unicode 4) not char[], to be most
convenient for "higher up" APIs like automaton? If we did char[] you'd still have to handle
surrogates process (and then it's not unlike doing byte[]).

nope. because unicode and java are optimized for UTF-16, not UTF-32. so we should use char[],
but use the codePoint apis, which are designed such that you can process text in UTF-16 (char[])
efficiently, yet also handle the rare case of supp. characters.
char[] is correct, its just that we have to be careful to use the right apis for processing
it.
With String() a lot of the apis such as String.toLowerCase do this automatically for you,
so most applications have no issues.


> 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.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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