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From "Christopher Morris (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-2035) TokenSources.getTokenStream() does not assign positionIncrement
Date Thu, 05 Nov 2009 13:41:35 GMT
TokenSources.getTokenStream() does not assign positionIncrement
---------------------------------------------------------------

                 Key: LUCENE-2035
                 URL: https://issues.apache.org/jira/browse/LUCENE-2035
             Project: Lucene - Java
          Issue Type: Bug
          Components: contrib/highlighter
    Affects Versions: 2.9, 2.4.1, 2.4
            Reporter: Christopher Morris


TokenSources.StoredTokenStream does not assign positionIncrement information. This means that
all tokens in the stream are considered adjacent. This has implications for the phrase highlighting
in QueryScorer when using non-contiguous tokens.

For example:
Consider  a token stream that creates tokens for both the stemmed and unstemmed version of
each word - the fox (jump|jumped)
When retrieved from the index using TokenSources.getTokenStream(tpv,false), the token stream
will be - the fox jump jumped

Now try a search and highlight for the phrase query "fox jumped". The search will correctly
find the document; the highlighter will fail to highlight the phrase because it thinks that
there is an additional word between "fox" and "jumped". If we use the original (from the analyzer)
token stream then the highlighter works.

Also, consider the converse - the fox did not jump
"not" is a stop word and there is an option to increment the position to account for stop
words - (the,0) (fox,1) (did,2) (jump,4)
When retrieved from the index using TokenSources.getTokenStream(tpv,false), the token stream
will be - (the,0) (fox,1) (did,2) (jump,3).

So the phrase query "did jump" will cause the "did" and "jump" terms in the text "did not
jump" to be highlighted. If we use the original (from the analyzer) token stream then the
highlighter works correctly.

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