Got it, make sense. Thanks Adrien. 2018-04-13 19:16 GMT+08:00 Adrien Grand <jpou...@gmail.com>:
> Queries should be fine: they are required to produce sorted iterators since > 5.0 when we removed the accetDocsOutOfOrder option on collectors. > > Le ven. 13 avr. 2018 à 13:10, Yonghui Zhao <zhaoyong...@gmail.com> a > écrit : > > > I can sort doc id and then fetch field via docvalue. > > > > but another big scenario for field cache is in custom score query, we > use > > field cache to compute score, stored fields can't work here for > performance > > issue. > > > > If I still use docvalue, I must make sure all queries are scored in > order, > > I think this will introduce some performance drop？ > > > > 2018-04-13 17:15 GMT+08:00 Adrien Grand <jpou...@gmail.com>: > > > > > Performance may be worse with stored fields indeed. In general Lucene > > makes > > > the assumption that millions of documents are queried but only ~100 > > > documents are retrieved in the end, so the bottleneck should be query > > > processing, not retrieving stored fieds. > > > > > > Le ven. 13 avr. 2018 à 05:27, Yonghui Zhao <zhaoyong...@gmail.com> a > > > écrit : > > > > > > > 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 <jpou...@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 <zhaoyong...@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? > > > > > > > > > > > > > > > > > > > > >
