thanks Adrien for the explanation, it's really much appreciated. I have written a quick test to reproduce the slower sorting with numeric DV. In this test case, it happens only when reverse sorting.
About the sorting by page i mentioned, it was due to a mistake in our testcase, sorry about that. I will make sure to test in a simpler environment next time ;) On Tue, Jul 30, 2013 at 3:13 PM, Adrien Grand <jpou...@gmail.com> wrote: > Hi, > > On Tue, Jul 30, 2013 at 8:19 PM, Nicolas Guyot <sfni...@gmail.com> wrote: > > When sorting numerically, the search seems to take a bit of a while > > compared to the lexically sorted search. > > Also when sorting numerically the result is sorted within each page but > no > > globally as opposed to the lexical sorted search. > > > > From my understanding, a SortedDocValuesField is sorted while indexing > but > > not the NumericDocValuesField which is why we are facing those issues in > > our implementation. Is that correct ? > > Sorted doc values are not exactly sorted, but Lucene computes all > unique values, sorts them and assigns an ordinal to every unique > value. These ordinals are then used at searching time to sort > documents. When comparing documents on the same segment, Lucene > directly uses the ordinals while when there are documents from > different documents to compare, Lucene uses the values themselves > (slower). > > I would expect sorting on a NumericDocValuesField to be faster since > longs can be used to directly compare documents across all segments. > Moreover, it is not normal that data is only sorted per page. Can you > write a small piece of code that reproduces the problem? > > -- > Adrien > > --------------------------------------------------------------------- > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > For additional commands, e-mail: java-user-h...@lucene.apache.org > >
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