Details

    • Type: Improvement
    • Status: Closed
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 4.0-ALPHA
    • Component/s: core/index
    • Labels:
      None
    • Lucene Fields:
      New

      Description

      Solr's UnInvertedField lets you quickly lookup all terms ords for a
      given doc/field.

      Like, FieldCache, it inverts the index to produce this, and creates a
      RAM-resident data structure holding the bits; but, unlike FieldCache,
      it can handle multiple values per doc, and, it does not hold the term
      bytes in RAM. Rather, it holds only term ords, and then uses
      TermsEnum to resolve ord -> term.

      This is great eg for faceting, where you want to use int ords for all
      of your counting, and then only at the end you need to resolve the
      "top N" ords to their text.

      I think this is a useful core functionality, and we should move most
      of it into Lucene's core. It's a good complement to FieldCache. For
      this first baby step, I just move it into core and refactor Solr's
      usage of it.

      After this, as separate issues, I think there are some things we could
      explore/improve:

      • The first-pass that allocates lots of tiny byte[] looks like it
        could be inefficient. Maybe we could use the byte slices from the
        indexer for this...
      • We can improve the RAM efficiency of the TermIndex: if the codec
        supports ords, and we are operating on one segment, we should just
        use it. If not, we can use a more RAM-efficient data structure,
        eg an FST mapping to the ord.
      • We may be able to improve on the main byte[] representation by
        using packed ints instead of delta-vInt?
      • Eventually we should fold this ability into docvalues, ie we'd
        write the byte[] image at indexing time, and then loading would be
        fast, instead of uninverting

        Attachments

        1. byte_size_32-bit-openjdk6.txt
          3 kB
          Mark Miller
        2. LUCENE-3003.patch
          88 kB
          Michael McCandless
        3. LUCENE-3003.patch
          77 kB
          Michael McCandless

          Issue Links

            Activity

              People

              • Assignee:
                mikemccand Michael McCandless
                Reporter:
                mikemccand Michael McCandless
              • Votes:
                0 Vote for this issue
                Watchers:
                4 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved: