Joel Bernstein <joels...@gmail.com> wrote: > I've tested with the Direct docValuesFormat which is uncompressed > in-memory. But I haven't seen any noticeable performance gain. I've been > meaning to dig into exactly why I wasn't seeing a performance gain, but > haven't had the chance to do this yet.
If this is about Direct PackedInts (1 entry in an underlying array = 1 value) vs. Packed PackedInts (bits must be shifted and masked out from the underlying array), then there is little time difference when retrieving values. I think this is caused by memory access being slow and computation being fast. It was discussed in Solr-4096. There is still some old and very poorly labeled charts at http://ekot.dk/misc/packedints/ Thinking out loud, I seem to remember some talk about the current PackedInts-using docValues code being hard for the JVM to inline? Could the problem be the number of indirections for a lookup, rather than the underlying data structure? - Toke Eskildsen
