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From Yonghui Zhao <zhaoyong...@gmail.com>
Subject Re: what's replacement of FieldCache in Lucene 7
Date Fri, 13 Apr 2018 03:27:01 GMT
My case is when I get some docs from lucene, I need also get some field
value of the retrieved docs.

For example  in lucene 4, I use FieldCache like this.

FieldCache.DEFAULT.getTerms(reader, name, false).get(locDocId).utf8ToString();

FieldCache.DEFAULT.getInts(reader, name, false).get(locDocId);

FieldCache.DEFAULT.getDoubles(reader, name, false).get(locDocId);


while docId may be not in ascending order.

Of course I can use stored field like this

Document doc = indexSearcher.doc(docId, storedFields.keySet());


But the performance should be worse than FieldCache.


2018-04-12 19:57 GMT+08:00 Adrien Grand <jpountz@gmail.com>:

> Hello,
>
> Doc values should be used instead of the field cache indeed. Note that this
> require to add them to your documents at index time, eg. with a
> NumericDocValuesField.
>
> Regarding random access, maybe you can use the advanceExact API, which
> exists on all doc-value iterators. Just make sure to never call it on
> decreasing doc IDs. If that doesn't work for you, can you describe you
> use-case, maybe there are better ways to implement what you need.
>
> Le jeu. 12 avr. 2018 à 13:54, Yonghui Zhao <zhaoyonghui@gmail.com> a
> écrit :
>
> > Hi,
> >
> > I am upgrading my project from Lucene 4 to 7.
> >
> > FieldCache is removed in lucene 7,  DocValue is replacement?
> >
> > But seems DocValue doesn't support random access.
> >
> > I need random access to get some specified field value quickly.
> >
> > So how to solve it?
> >
>

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