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Posted to java-user@lucene.apache.org by Toph <ch...@gmail.com> on 2008/07/01 01:13:55 UTC
Re: Incorrect Token Offset when using multiple fieldable instance
Interesting discussion... glad I'm not the only one with this challenge.
Michael McCandless-2 wrote:
>
> EG, if you use Highlighter on a
> multi-valued field indexed with stored field & term vectors and say
> the first field ended with a stop word that was filtered out, then
> your offsets will be off and the wrong parts will be highlighted
>
I found this post by attempting just this exact thing, and I can confirm,
that yes, the offsets are incorrect for all but the first instance of the
field in the document, so they are useless for highlighting. I tried
concatenating all instances of the fields, but of course if an instance of
the field ended with punctuation or a stop word, those characters were not
added to the offset. I'll try the suggested workaround re adding a false
term at the end of each field, but a better API would be if "offset" became
a pair of ints, first being the index of the Field for getFields(name) and
the second being the offset in that instance of the field.
Christopher
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Re: Incorrect Token Offset when using multiple fieldable instance
Posted by Michael McCandless <lu...@mikemccandless.com>.
Toph wrote:
> Michael McCandless-2 wrote:
>>
>>
>> We could alternatively extend TokenStream so you could query it for
>> the final offset, then fix indexing to use that value instead of the
>> endOffset of the last token that it saw.
>>
>>
>
> Querying the tokenstream for the final offset would good, but then
> would the
> change be put into the DocumentWriter directly or available as an
> option?
I would put the change into DocumentsWriter directly (ie running by
default) with an option to enable the old (buggy) behavior for those
apps that have workarounds and want to get back to the back-compatible
behavior.
Mike
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Re: Incorrect Token Offset when using multiple fieldable instance
Posted by Toph <ch...@gmail.com>.
Michael McCandless-2 wrote:
>
>
> This would actually be a fairly large change: it's a change to the
> index format and all APIs that handle offsets during indexing &
> searching/retrieving.
>
>
For now I just changed the offset calculation in DocumentWriter as specified
here by the OP:
> replace DocumentWriter$FieldData#invertField offset = offsetEnd+1; by
> offset = stringValue.length();
>
It has side effects as previously mentioned on this list, e.g. if the
tokenstream is not backed by a stringValue or the Analyzer does not
calculate offsets in the normal way. But for my purposes it works.
This issue was also discussed previously
http://lucene.markmail.org/search/?q=offset%20documentwriter#query:offset%20documentwriter+page:1+mid:l6jbfmfisyg5zyre+state:results
here .
Michael McCandless-2 wrote:
>
>
> We could alternatively extend TokenStream so you could query it for
> the final offset, then fix indexing to use that value instead of the
> endOffset of the last token that it saw.
>
>
Querying the tokenstream for the final offset would good, but then would the
change be put into the DocumentWriter directly or available as an option?
Chris
--
View this message in context: http://www.nabble.com/Incorrect-Token-Offset-when-using-multiple-fieldable-instance-tp15833468p18238566.html
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Re: Incorrect Token Offset when using multiple fieldable instance
Posted by Michael McCandless <lu...@mikemccandless.com>.
This would actually be a fairly large change: it's a change to the
index format and all APIs that handle offsets during indexing &
searching/retrieving.
We could alternatively extend TokenStream so you could query it for
the final offset, then fix indexing to use that value instead of the
endOffset of the last token that it saw.
Mike
Toph wrote:
>
> Interesting discussion... glad I'm not the only one with this
> challenge.
>
>
> Michael McCandless-2 wrote:
>>
>> EG, if you use Highlighter on a
>> multi-valued field indexed with stored field & term vectors and say
>> the first field ended with a stop word that was filtered out, then
>> your offsets will be off and the wrong parts will be highlighted
>>
>
> I found this post by attempting just this exact thing, and I can
> confirm,
> that yes, the offsets are incorrect for all but the first instance
> of the
> field in the document, so they are useless for highlighting. I tried
> concatenating all instances of the fields, but of course if an
> instance of
> the field ended with punctuation or a stop word, those characters
> were not
> added to the offset. I'll try the suggested workaround re adding a
> false
> term at the end of each field, but a better API would be if "offset"
> became
> a pair of ints, first being the index of the Field for
> getFields(name) and
> the second being the offset in that instance of the field.
>
> Christopher
> --
> View this message in context: http://www.nabble.com/Incorrect-Token-Offset-when-using-multiple-fieldable-instance-tp15833468p18206216.html
> Sent from the Lucene - Java Users mailing list archive at Nabble.com.
>
>
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