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https://issues.apache.org/jira/browse/LUCENE-7719?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Smiley updated LUCENE-7719:
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Attachment: LUCENE_7719.patch
Here is a patch for consideration.
First of all, I realized that this bug is very minor because only _some_
{{AutomatonQuery.getAutomaton}} are binary (I thought they all were); others
are char based. The ones that are binary in Lucene are {{PrefixQuery}} and
{{TermRangeQuery}}, both of which are special cased in
{{MultiTermHighlighting}}. So practically speaking I think the only users to
see this bug would be anyone building a custom AutomatonQuery. Nonetheless
this should be cleaned up and actually tested.
The patch:
* Adds a fairly thorough test with lots of randomized unicode, testing
PrefixQuery, TermRangeQuery, WildcardQuery, and FuzzyQuery
* removes the special casing of AutomatonQuery subclasses in
MultiTermHighlighting. AQ is handled generically now.
* added {{AutomatonQuery.isAutomatonBinary()}} with a new field to match.
* if the AQ.getAutomaton is _not_ binary, we follow a simple/obvious path
* if the automaton is binary, then I produce a CharRunAutomaton implementing
run() to navigate the Automaton char by char. It makes a BytesRunAutomaton on
the automaton. I inlined the one and two byte UTF char logic from
{{UnicodeUtil.UTF16toUTF8}}. If the char needs more bytes, then I call out to
UTF16toUTF8 and work off the generated byte array for the remaining chars. I
think this is more maintainable, albeit slower, than reproducing the logic.
There is a TODO on making the BytesRunAutomaton on the binary Automaton. This
is redundant since the AutomatonQuery already has a compiledAutomaton which in
turn already has a BytesRunAutomaton. The construction cost seems less than
trivial as it determinizes the automaton and does other work. Is this a big
deal? It seems kinda sorta; it depends.
> UnifiedHighlighter doesn't handle some AutomatonQuery's with multi-byte chars
> -----------------------------------------------------------------------------
>
> Key: LUCENE-7719
> URL: https://issues.apache.org/jira/browse/LUCENE-7719
> Project: Lucene - Core
> Issue Type: Bug
> Components: modules/highlighter
> Reporter: David Smiley
> Assignee: David Smiley
> Attachments: LUCENE_7719.patch
>
>
> In MultiTermHighlighting, a CharacterRunAutomaton is being created that takes
> the result of AutomatonQuery.getAutomaton that in turn is byte oriented, not
> character oriented. For ASCII terms, this is safe but it's not for
> multi-byte characters. This is most likely going to rear it's head with a
> WildcardQuery, but due to special casing in MultiTermHighlighting,
> PrefixQuery isn't affected. Nonetheless it'd be nice to get a general fix in
> so that MultiTermHighlighting can remove special cases for PrefixQuery and
> TermRangeQuery (both subclass AutomatonQuery).
> AFAICT, this bug was likely in the PostingsHighlighter since inception.
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