Queries cannot be ordered "sequentially". Let's say that you run 3 Queries, w/ one term each "a", "b" and "c". On disk, the posting lists of the terms can look like this: post1(a), post1(c), post2(a), post1(b), post2(c), post2(b) etc. They are not guaranteed to be consecutive. The code makes sure the posting list parts come logically one after the others, by file-system-wise, they can be completely messed up on disk.
Besides, I'm not sure that what you want will get you anything. If you run 3 queries in parallel, you open 3 file descriptors (at least). Modern machines can very well read 3 files in parallel, so you won't be seeking around as much as you think. I just don't think that application-wise there's something you can do, at least in this case. Shai On Wed, Jul 22, 2009 at 8:15 PM, tsuraan <tsur...@gmail.com> wrote: > > It's not accurate to say that Lucene scans the index for each search. > > Rather, every Query reads a set of posting lists, each are typically read > > from disk. If you pass Query[] which have nothing to do in common (for > > example no terms in common), then you won't gain anything, b/c each Query > > will already read just the posting lists it needs. > > That sounds like a lot of disk seeking, if the terms associated with > each query don't happen to fall in exact order. My disks can sustain > 100+ MB/s sequential read, but if they're seeking that number > plummets. Would it be possible to order the queries so that they can > each read their index information in order, to minimize thrashing? > > > If your Query[] contains the exact Query, it's redundant to run all these > > searches, since they will return the same results every time. > > I'm assuming that the queries being run are different. Caching query > results would be pretty easy for us though, so if the queries aren't > different, they could be made to be. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > For additional commands, e-mail: java-user-h...@lucene.apache.org > >
