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From Marc F <xfrontli...@gmail.com>
Subject Re: Incorrect CollectionStatistics if IndexWriter.close is not called
Date Tue, 02 Mar 2021 09:34:28 GMT
I'm indexing medical documents, and documents on emerging topics are
updated quite often.
For example, right now, "COVID" will be overrepresented in my index
because deleted documents are still counted, and then a "COVID" query
will have a lower score than a query on a "unfashionable" topic,
because the idf also takes into account the "number of documents
containing term".

I did not expect this behaviour but I can understand that it's needed
for performance reasons and the only thing I can think of to have
accurate scoring, it's to reindex my documents more often and I don't
always have this luxury.

Thanks for your replies :)

Le lun. 1 mars 2021 à 20:47, Diego Ceccarelli (BLOOMBERG/ LONDON)
<dceccarelli4@bloomberg.net> a écrit :
>
> I'm not sure that closing and opening the index writer will always work - I think the
'problem' will be solved once the segment with the deleted document  will be merged with another
segment - that might happen during the close but might also *not* happen (e.g., if you have
only one segment, and you delete, probably closing/opening won't fix).
>
> Can you describe your problem that you are trying to solve? why do you need such accuracy?
if this is for some type of scoring the ranking shouldn't be affected if you have X or X-1
documents in the collection...
>
> Cheers,
> diego
>
> From: java-user@lucene.apache.org At: 03/01/21 16:23:48To:  Diego Ceccarelli (BLOOMBERG/
LONDON ) ,  java-user@lucene.apache.org
> Subject: Re: Incorrect CollectionStatistics if IndexWriter.close is not called
>
> Hi,
>
> You're right the documentation of Terms.getDocCount says that "this
> measure does not take deleted documents into account".
> So if we want correct counts and correct query scores, the IndexWriter
> has to be closed after documents are deleted/updated and a new one has
> to be created when new documents arrive.
>
> Thanks
>
> Le dim. 28 févr. 2021 à 17:04, Diego Ceccarelli (BLOOMBERG/ LONDON)
> <dceccarelli4@bloomberg.net> a écrit :
> >
> > I *guess* it's due to the fact that the update is implemented as remove and
> reinsert the document. Deletes in Lucene are lazy: the deleted document is just
> flagged as deleted in a bitmap and then removed from the index only when
> segments are merged.  Did you check IndexSearcher.collectionStatistic
> documentation? it should mention something about that..
> >
> > Cheers,
> > diego
> >
> >
> > From: java-user@lucene.apache.org At: 02/28/21 11:09:52To:
> java-user@lucene.apache.org
> > Subject: Incorrect CollectionStatistics if IndexWriter.close is not called
> >
> > Hi,
> >
> > I don't understand if I'm doing something wrong or if it is the
> > expected behaviour.
> >
> > My problem is when a document is updated the collectionStatistics
> > returns counts as if a new document is added in the index, even after
> > a call to IndexWriter.commit and to
> > SearcherManager.maybeRefreshBlocking.
> > If I call the IndexWriter.close, the counts are correct again, but the
> > documentation of IndexWriter.close says to try to reuse the
> > IndexWriter so I'm a bit confused.
> >
> > Ex:
> > If I add two documents to an empty index
> >
> > IndexSearcher.collectionStatistics("TEXT")) returns
> > "field="TEXT",maxDoc=2,docCount=2,sumTotalTermFreq=5,sumDocFreq=5" ->
> > OK
> >
> > then I update one of the document and call commit()
> >
> > IndexSearcher.collectionStatistics("TEXT")) returns
> > "field="TEXT",maxDoc=3,docCount=3,sumTotalTermFreq=9,sumDocFreq=9" ->
> > NOK
> >
> > If I call close() now
> >
> > IndexSearcher.collectionStatistics("TEXT")) returns
> > "field="TEXT",maxDoc=2,docCount=2,sumTotalTermFreq=6,sumDocFreq=6" ->
> > OK
> >
> > Note that the counts are correct if the index contains only one document.
> >
> >
> > I attached a test case.
> >
> > Am I doing something wrong somewhere?
> >
> >
> > Julien
> >
> >
> > ----------------------------
> >
> >
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> >
> >
>
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