lucene at mikemccandless
Jul 9, 2008, 7:42 AM
Post #2 of 2
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Re: Retrieving term positions without storing the term vectors
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Indeed Lucene stores position information and uses that when doing
phrase queries. It is stored separately from term vectors.
However, the positions are "inverted" meaning for a given term you can
find all documents that had that term, as well as the positions where
that term had occurred in the documents. So, because of this
inversion, it's not easily reconstructed into all terms & their
positions that occurred in a document. It is feasible to do so, but
the amount of computation/IO really makes it unrealistic in most
situations. This is why term vectors (they are not inverted) are used
when you want to retrieve all terms/positions/offsets for a single
document.
Mike
PS -- it's better to use java-user mailing list for this sort of
question.
syga wrote:
>
> Dear all,
>
> Am I correct to believe that a quoted (phrase) search, like "red
> dog",
> returns documents containing the consecutive words "red" and "dog"
> in that
> order, even without storing the term vector (Field.TermVector.NO)?
>
> If the inverted index (with Field.TermVector.NO and
> Field.Store.NO) is
> able to check whether the words are consecutive and in the right
> order, then
> I suppose that the inverted index must somehow contain the positional
> information of the words in the documents.
>
> If my supposition is correct, then is it possible to access this
> positional information via the Lucene API? Of course, I am not
> speaking
> about indexReader.getTermFreqVector(doc, field), which returns null
> if we
> use Field.TermVector.NO.
>
> If my supposition is incorrect, could you please explain how the
> inverted
> index is able to deal with quoted searches without having this
> positional
> information?
>
> Thank you so much,
> SG.
> --
> View this message in context: http://www.nabble.com/Retrieving-term-positions-without-storing-the-term-vectors-tp18359432p18359432.html
> Sent from the Lucene - General mailing list archive at Nabble.com.
>
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