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https://issues.apache.org/jira/browse/LUCENE-10610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17552947#comment-17552947
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Robert Muir commented on LUCENE-10610:
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and for the same reason, again, we can do something else for runautomaton too.
Such as remove hashCode/equals methods entirely and let it be defined by
identity. it is perfectly reasonable just like it is for automaton.
maybe some tests have to be changed or modified to use
{{Operations.sameLanguage}} for assertions instead of {{equals()}}, that's fine.
> RunAutomaton#hashCode() can easily cause hash collision for different
> Automatons
> --------------------------------------------------------------------------------
>
> Key: LUCENE-10610
> URL: https://issues.apache.org/jira/browse/LUCENE-10610
> Project: Lucene - Core
> Issue Type: Bug
> Reporter: Tomoko Uchida
> Priority: Minor
>
> Current RunAutomaton#hashCode() is:
> {code:java}
> @Override
> public int hashCode() {
> final int prime = 31;
> int result = 1;
> result = prime * result + alphabetSize;
> result = prime * result + points.length;
> result = prime * result + size;
> return result;
> }
> {code}
> Since it does not take account of the contents of the {{points}} array, this
> returns the same value for different automatons when their alphabet size and
> state size are the same.
> For example, this test code passes.
> {code:java}
> public void testHashCode() throws IOException {
> PrefixQuery q1 = new PrefixQuery(new Term("field", "aba"));
> PrefixQuery q2 = new PrefixQuery(new Term("field", "fee"));
> assert q1.compiled.runAutomaton.hashCode() ==
> q2.compiled.runAutomaton.hashCode();
> }
> {code}
> I suspect this is a bug?
> Note that I think it's not a serious one; all callers of this {{hashCode()}}
> take account of additional information when calculating their own hash value,
> it seems there is no substantial impact on higher-level APIs.
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