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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1448) add getFinalOffset() to TokenStream
Date Sat, 06 Dec 2008 09:51:44 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12654044#action_12654044
] 

Michael Busch commented on LUCENE-1448:
---------------------------------------

{quote}
But: you'd still need a way in this model to serialize finalOffset, once,
at the end?
{quote}

Maybe we can introduce an abstract EndOfStreamAttribute and 
FinalOffsetAttribute and FinalPosIncrAttribute that extend EOSA.

Then in a stream like CachingTokenFilter a AttributeAcceptor can
be used that doesn't accept attributes of type EOSA in increment().

In end() it would use an AttributeAcceptor that accepts EOSA atts
and cache those.

{quote}
OK I'm gonna assign this one to you, Michael ;)
{quote}

Bummer! Why did I say anything? ;) j/k

> 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 Busch
>            Priority: Minor
>             Fix For: 2.9
>
>         Attachments: LUCENE-1448.patch, LUCENE-1448.patch, LUCENE-1448.patch, LUCENE-1448.patch
>
>
> 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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