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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-1448) add getFinalOffset() to TokenStream
Date Tue, 11 Nov 2008 09:28:44 GMT
add getFinalOffset() to TokenStream
-----------------------------------

                 Key: LUCENE-1448
                 URL: https://issues.apache.org/jira/browse/LUCENE-1448
             Project: Lucene - Java
          Issue Type: Bug
          Components: Analysis
            Reporter: Michael McCandless
            Assignee: Michael McCandless
             Fix For: 2.9


If you add multiple Fieldable instances for the same field name to a document, and you then
index those fields with TermVectors storing offsets, it's very likely the offsets for all
but the first field instance will be wrong.

This is because IndexWriter under the hood adds a cumulative base to the offsets of each field
instance, where that base is 1 + the endOffset of the last token it saw when analyzing that
field.

But this logic is overly simplistic.  For example, if the WhitespaceAnalyzer is being used,
and the text being analyzed ended in 3 whitespace characters, then that information is lost
and then next field's offsets are then all 3 too small.  Similarly, if a StopFilter appears
in the chain, and the last N tokens were stop words, then the base will be 1 + the endOffset
of the last non-stopword token.

To fix this, I'd like to add a new getFinalOffset() to TokenStream.  I'm thinking by default
it returns -1, which means "I don't know so you figure it out", meaning we fallback to the
faulty logic we have today.

This has come up several times on the user's list.

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