Thank you very much for answering me. But could you explain how Lucene reads the doc values files sequentially?
2016-05-30 18:15 GMT+08:00 Adrien Grand <jpou...@gmail.com>: > Doc values indeed need to read from disk. However, the fact that Lucene > reads the doc values files sequentially (disks perform better at sequential > access than random access) and that the filesystem cache helps keep hot > regions of the doc values files in memory usually helps keep perfermance > close to what we would get if the data was stored in memory. > > Le lun. 30 mai 2016 à 12:01, Ting Yao <ting.echo....@gmail.com> a écrit : > > > Hi all, > > I am reading Lucene source code recently and we also use the > Elastic > > Search as our search engine. As far as I know, the elastic search > > performance is pretty good. The elastic search is based on Lucene. So I > am > > wondering that how it can search words so fast when the field data > > (uninverted index) are stored in disk. > > The DocValues make access filed values fast. From my perspective， > it's > > of course fast when few values of a field are read. But when few fields > > need to access, I think it's not fast again. Because when access a field, > > all of its doc values need to read with MMap. So the system needs to read > > disk to load the data. > > So could anyone help me understand the DocValues operating mechanism? > > > > Echo Yao > > > -- Echo Yao
