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From Michael McCandless <luc...@mikemccandless.com>
Subject Re: Difference in Retrieving values of a docvalue field using atomicreader over duplicate StoredField
Date Wed, 01 Jun 2016 21:08:16 GMT
Well, each access may involve disk seeks (if the pages are not already hot
in the OS's IO cache).

So if you do some doc values + some stored fields you're looking at
multiple seeks per docID you retrieve.

Really you should only do this for a few hits, e.g. one page worth.

Mike McCandless

http://blog.mikemccandless.com

On Wed, Jun 1, 2016 at 3:15 PM, Kumaran Ramasubramanian <kums.134@gmail.com>
wrote:

> Hi All,
>
>
> In javadoc of every docvalue field
> <
> https://lucene.apache.org/core/4_10_4/core/org/apache/lucene/document/SortedNumericDocValuesField.html
> >,
> there is line like
>
> ​
> > If you also need to store the value, you should add a separate
> StoredField
> > <
> https://lucene.apache.org/core/4_10_4/core/org/apache/lucene/document/StoredField.html
> >
> >  instance.​
>
>
>
> https://lucene.apache.org/core/4_10_4/core/org/apache/lucene/document/SortedNumericDocValuesField.html
>
>
>
>
> But, we are able to retrieve the value of SortedNumericDocValuesField
> using AtomicReader also
>
> for (AtomicReaderContext context : indexReader.leaves())
> > {
> >  AtomicReader atomicReader = context.reader();
> >  SortedNumericDocValues
> >  sortedDocValues=DocValues.getSortedNumeric(atomicReader, "Numeric
> > ​_docvalue​
> > _price");
> > }
>
>
> ​So what is the difference actually? Is there any performance or time taken
> issue in retrieving values of a docvalue field using atomicreader over
> StoredField? ​
>
> Please clarify me what am i missing?​
>
> Thanks in advance
>
>
> ​--​
>
> Kumaran R
>

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