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https://issues.apache.org/jira/browse/LUCENE-8102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16295157#comment-16295157
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Robert Muir commented on LUCENE-8102:
-------------------------------------
Also here are few more ideas:
* There is a TODO in the code regarding using found sink state... a method
findSinkState was added here and is actually called, but its not used to
determine whether or not common suffix should be computed, but only if this
really works (there should be some tests)
* The optimization could be guarded with a state count check maybe (something
absurd).
Either way, I think its really important not to regress on common "stupid
simple" queries like leading wildcards.
> CompiledAutomaton performance for determining common suffix
> -----------------------------------------------------------
>
> Key: LUCENE-8102
> URL: https://issues.apache.org/jira/browse/LUCENE-8102
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/FSTs
> Affects Versions: 7.1
> Reporter: Thomas Poppe
>
> We're using the automaton package as part of Elasticsearch for doing regexp
> queries. Our business requires us to process rather complex regular
> expressions, for example (we have more complex examples, but this one
> illustrates the problem):
> {noformat}
> (¦.)*(¦?[^¦]){1,10}ab(¦.)*(¦?[^¦]){1,10}c(¦.)*(¦?[^¦]){1,10}d
> {noformat}
> With a large enough value of maxDeterminizedStates, this works. The problem
> we're having is that the conversion of this regular expression to a
> CompiledAutomaton takes very long. Almost all of the time goes into
> determining the common suffix for the Automaton (which is "d" in this
> example) - calculated with a call to Operations.getCommonSuffixBytesRef.
> This suffix is only used as an optimization. Skipping the calculation of
> this suffix allows us to process these kinds of queries.
> - Would it be possible to introduce a way to skip the calculation of this
> common suffix (ideally something we control from within our query to
> Elasticsearch)?
> - Or would it be possible to take a look at this getCommonSuffixBytesRef
> operation, to see if it can be optimized? Most of the time goes to
> determinizing the reversed automaton - maybe this can be avoided somehow?
> Reaction from Mike McCandless on the mailing list:
> This is just an optimization; maybe we should expose an option to disable it?
> Or maybe we can find the common suffix on an NFA instead, to avoid
> determinization?
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