Alan Woodward created LUCENE-8916:
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Summary: GraphTokenStreamFiniteStrings.FiniteStringsTokenStream
does not play well with subsequent TokenFilters
Key: LUCENE-8916
URL: https://issues.apache.org/jira/browse/LUCENE-8916
Project: Lucene - Core
Issue Type: Improvement
Reporter: Alan Woodward
Assignee: Alan Woodward
GraphTokenStreamFiniteStrings provides a view over multiple paths through a
Token graph, which is useful when building queries over multiple length
synonyms. This view is exposed as an iterator over simple TokenStreams.
However, these TokenStreams do not work correctly when further wrapped in token
filters, because they do not use a CharTermAttribute.
For an example of issues this can cause, see
https://github.com/elastic/elasticsearch/issues/43976, where elasticsearch uses
a special shingle field to speed up phrase searches. Queries are converted to
shingles if they have multiple terms. However, if the query resolves into a
graph due to synonyms, then this conversion breaks because the
FixedShingleFilter is given a token stream built by GTSFS; terms are set using
BytesTermAttribute, but then read using CharTermAttribute, and as these have
different backing implementations, FSF ends up emitting null tokens.
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