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https://issues.apache.org/jira/browse/LUCENE-6046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14194413#comment-14194413
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Dawid Weiss commented on LUCENE-6046:
-------------------------------------
I didn't mean to imply we should change the regexp implementation! :) This was
just a pointer in case somebody wished to understand why regexps can explode. I
actually wish there was an NFA-based regexp implementation for Java (with
low-memory footprint) because this would make concatenating thousands of
regexps (e.g., for pattern detection) much easier.
> RegExp.toAutomaton high memory use
> ----------------------------------
>
> Key: LUCENE-6046
> URL: https://issues.apache.org/jira/browse/LUCENE-6046
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/queryparser
> Affects Versions: 4.10.1
> Reporter: Lee Hinman
> Assignee: Michael McCandless
> Priority: Minor
>
> When creating an automaton from an org.apache.lucene.util.automaton.RegExp,
> it's possible for the automaton to use so much memory it exceeds the maximum
> array size for java.
> The following caused an OutOfMemoryError with a 32gb heap:
> {noformat}
> new
> RegExp("\\[\\[(Datei|File|Bild|Image):[^]]*alt=[^]|}]{50,200}").toAutomaton();
> {noformat}
> When increased to a 60gb heap, the following exception is thrown:
> {noformat}
> 1> java.lang.IllegalArgumentException: requested array size 2147483624
> exceeds maximum array in java (2147483623)
> 1>
> __randomizedtesting.SeedInfo.seed([7BE81EF678615C32:95C8057A4ABA5B52]:0)
> 1> org.apache.lucene.util.ArrayUtil.oversize(ArrayUtil.java:168)
> 1> org.apache.lucene.util.ArrayUtil.grow(ArrayUtil.java:295)
> 1>
> org.apache.lucene.util.automaton.Automaton$Builder.addTransition(Automaton.java:639)
> 1>
> org.apache.lucene.util.automaton.Operations.determinize(Operations.java:741)
> 1>
> org.apache.lucene.util.automaton.MinimizationOperations.minimizeHopcroft(MinimizationOperations.java:62)
> 1>
> org.apache.lucene.util.automaton.MinimizationOperations.minimize(MinimizationOperations.java:51)
> 1> org.apache.lucene.util.automaton.RegExp.toAutomaton(RegExp.java:477)
> 1> org.apache.lucene.util.automaton.RegExp.toAutomaton(RegExp.java:426)
> {noformat}
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