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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2620) Queries with too many asterisks causing 100% CPU usage
Date Tue, 24 Aug 2010 16:43:16 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12901960#action_12901960
] 

Robert Muir commented on LUCENE-2620:
-------------------------------------

Hello Nick, thanks for your patch.

In trunk this is no problem, because wildcard query works in a very different way and both
foo**********bar and foo*bar are compiled to the same matcher:
{noformat}
    WildcardQuery wq = new WildcardQuery(new Term("foo", "foo*******bar"));
    WildcardQuery wq2 = new WildcardQuery(new Term("foo", "foo*bar"));
    assertEquals(wq.automaton.getNumberOfStates(), wq2.automaton.getNumberOfStates());
    assertEquals(wq.automaton.getNumberOfTransitions(), wq2.automaton.getNumberOfTransitions());
{noformat}

But at a glance, your patch looks like a potentially useful optimization for 3.x


> Queries with too many asterisks causing 100% CPU usage
> ------------------------------------------------------
>
>                 Key: LUCENE-2620
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2620
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Search
>    Affects Versions: 3.0.1
>         Environment: Debian Lenny with Tomcat 5.5 and Mac OS X 10.6 with Tomcat 6, probably
others
>            Reporter: Nick Barkas
>         Attachments: lucene-asterisks.diff
>
>
> If a search query has many adjacent asterisks (e.g. fo**************obar), I can get
my webapp caught in a loop that does not seem to end in a reasonable amount of time and may
in fact be infinite. For just a few asterisks the query eventually does return some results,
but as I add more it takes a longer and longer amount of time. After about six or seven asterisks
the query never seems to finish. Even if I abort the search, the thread handling the troublesome
query continues running in the background and pinning a CPU.
> I found the problem in src/java/org/apache/lucene/search/WildcardTermEnum.java on Lucene
3.0.1 and it looks like 3.0.2 ought to be affected as well. I'm not sure about trunk, though.
I have a patch that fixes the problem for me in 3.0.1.

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