Hi Mike,

Thanks for your response.  I opened Jira issue 8102 for this 
(https://issues.apache.org/jira/browse/LUCENE-8102).  I included your 
suggestions below in the description of the issue.


From: Michael McCandless <luc...@mikemccandless.com>
Date: Sunday, 17 December 2017 at 14:19
To: Lucene Users <java-user@lucene.apache.org>, "Poppe, Thomas (IP&Science)" 
Subject: Re: CompiledAutomaton performance issue

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 

Can you open a Jira issue so we can discuss options?


Mike McCandless


On Fri, Dec 15, 2017 at 5:38 AM, Poppe, Thomas (IP&Science) 
<thomas.po...@clarivate.com<mailto:thomas.po...@clarivate.com>> wrote:

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):


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.

If my understanding is correct, this suffix is only used as an optimization (is 
this correct?).  Skipping the calculation of this suffix allows us to process 
these kinds of queries.

So here are my questions:
- 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 
- 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?
- Does anyone have any other suggestions?  We've tried to reduce the complexity 
of the query, but it is something we would really like to support.

Thomas Poppe

Reply via email to