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https://issues.apache.org/jira/browse/LUCENE-6046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14194406#comment-14194406
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Michael McCandless commented on LUCENE-6046:
--------------------------------------------
bq. Russ Cox wrote a series of excellent articles about different approaches
of implementing regexp scanners.
Thanks Dawid, these are great.
Switching to NFA based matching would be a very large change ... I don't think
we should pursue it here. Terms.intersect implementation for block tree is
already very complex ... though I suppose of we could hide the "on the fly
subset construction" (and convert regexp to a Thompson NFA) under an API, then
Terms.intersect implementation wouldn't have to change much.
Still, there will always be adversarial cases no matter which approach we
choose. I think for this issue we should allow passing in a "how much work are
you willing to do" to RegExp.toAutomaton, and it throws an exc when it would
exceed that.
> 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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