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  1. Lucene - Core
  2. LUCENE-3584

bulk postings should be codec private


    • Task
    • Status: Closed
    • Major
    • Resolution: Fixed
    • None
    • 4.0-ALPHA
    • None
    • None
    • New


      In LUCENE-2723, a lot of work was done to speed up Lucene's bulk postings read API.

      There were some upsides:

      • you could specify things like 'i dont care about frequency data up front'.
        This made things like multitermquery->filter and other consumers that don't
        care about freqs faster. But this is unrelated to 'bulkness' and we have a
        separate patch now for this on LUCENE-2929.
      • the buffersize for standardcodec was increased to 128, increasing performance
        for TermQueries, but this was unrelated too.

      But there were serious downsides/nocommits:

      • the API was hairy because it tried to be 'one-size-fits-all'. This made consumer code crazy.
      • the API could not really be specialized to your codec: e.g. could never take advantage that e.g. docs and freqs are aligned.
      • the API forced codecs to implement delta encoding for things like documents and positions.
        But this is totally up to the codec how it wants to encode! Some codecs might not use delta encoding.
      • using such an API for positions was only theoretical, it would have been super complicated and I doubt ever
        performant or maintainable.
      • there was a regression with advance(), probably because the api forced you to do both a linear scan thru
        the remaining buffer, then refill...

      I think a cleaner approach is to let codecs do whatever they want to implement the DISI
      contract. This lets codecs have the freedom to implement whatever compression/buffering they want
      for the best performance, and keeps consumers simple. If a codec uses delta encoding, or if it wants
      to defer this to the last possible minute or do it at decode time, thats its own business. Maybe a codec
      doesn't want to do any buffering at all.


        1. LUCENE-3584.patch
          38 kB
          Robert Muir



            rcmuir Robert Muir
            rcmuir Robert Muir
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