Class ValuesSource.Bytes.WithOrdinals.FieldData

Enclosing class:

public static class ValuesSource.Bytes.WithOrdinals.FieldData extends ValuesSource.Bytes.WithOrdinals
  • Field Details

  • Constructor Details

  • Method Details

    • bytesValues

      public SortedBinaryDocValues bytesValues(org.apache.lucene.index.LeafReaderContext context)
      Description copied from class: ValuesSource
      Get a byte array like view into the values. This is the "native" way to access ValuesSource.Bytes-style values.
      Specified by:
      bytesValues in class ValuesSource
    • ordinalsValues

      public org.apache.lucene.index.SortedSetDocValues ordinalsValues(org.apache.lucene.index.LeafReaderContext context)
      Description copied from class: ValuesSource.Bytes.WithOrdinals
      Get a view into the leaf's ordinals and their BytesRef values.

      Use DocValuesIterator.advanceExact(int), SortedSetDocValues.getValueCount(), and SortedSetDocValues.nextOrd() to fetch the ordinals. Use SortedSetDocValues.lookupOrd(long) to convert form the ordinal number into the BytesRef value. Make sure to copy the result if you need to keep it.

      Each leaf may have a different ordinal for the same byte array. Imagine, for example, an index where one leaf has the values "a", "b", "d" and another leaf has the values "b", "c", "d". "a" has the ordinal 0 in the first leaf and doesn't exist in the second leaf. "b" has the ordinal 1 in the first leaf and 0 in the second leaf. "c" doesn't exist in the first leaf and has the ordinal 1 in the second leaf. And "d" gets the ordinal 2 in both leaves.

      If you have to compare the ordinals of values from different segments then you'd need to somehow merge them. ValuesSource.Bytes.WithOrdinals.globalOrdinalsValues(org.apache.lucene.index.LeafReaderContext) provides such a merging at the cost of longer startup times when the index has been modified.

      Specified by:
      ordinalsValues in class ValuesSource.Bytes.WithOrdinals
    • globalOrdinalsValues

      public org.apache.lucene.index.SortedSetDocValues globalOrdinalsValues(org.apache.lucene.index.LeafReaderContext context)
      Description copied from class: ValuesSource.Bytes.WithOrdinals
      Get a "global" view into the leaf's ordinals. This can require construction of fairly large set of lookups in memory so prefer ValuesSource.Bytes.WithOrdinals.ordinalsValues(org.apache.lucene.index.LeafReaderContext) unless you need the global view.

      This functions just like ValuesSource.Bytes.WithOrdinals.ordinalsValues(org.apache.lucene.index.LeafReaderContext) except that the ordinals that SortedSetDocValues.nextOrd() and SortedSetDocValues.lookupOrd(long) operate on are "global" to all segments in the shard. They are ordinals into a lookup table containing all values on the shard.

      Compare this to the example in the docs for ValuesSource.Bytes.WithOrdinals.ordinalsValues(org.apache.lucene.index.LeafReaderContext). Imagine, again, an index where one leaf has the values "a", "b", "d" and another leaf has the values "b", "c", "d". The global ordinal for "a" is 0. The global ordinal for "b" is 1. The global ordinal for "c" is 2. And the global ordinal for "d" is, you guessed it, 3.

      This makes comparing the values from different segments much simpler. But it comes with a fairly high memory cost and a substantial performance hit when this method is first called after modifying the index. If the global ordinals lookup hasn't been built then this method's runtime is roughly proportional to the number of distinct values on the field. If there are very few distinct values then the runtime'll be dominated by factors related to the number of segments. But in that case it'll be fast enough that you won't usually care.

      Specified by:
      globalOrdinalsValues in class ValuesSource.Bytes.WithOrdinals
    • supportsGlobalOrdinalsMapping

      public boolean supportsGlobalOrdinalsMapping()
      Description copied from class: ValuesSource.Bytes.WithOrdinals
      Whether this values source is able to provide a mapping between global and segment ordinals, by returning the underlying OrdinalMap. If this method returns false, then calling ValuesSource.Bytes.WithOrdinals.globalOrdinalsMapping(org.apache.lucene.index.LeafReaderContext) will result in an UnsupportedOperationException.
      Specified by:
      supportsGlobalOrdinalsMapping in class ValuesSource.Bytes.WithOrdinals
    • globalOrdinalsMapping

      public LongUnaryOperator globalOrdinalsMapping(org.apache.lucene.index.LeafReaderContext context) throws IOException
      Description copied from class: ValuesSource.Bytes.WithOrdinals
      Returns a mapping from segment ordinals to global ordinals. This allows you to post process segment ordinals into global ordinals which could save you a few lookups. Also, operating on segment ordinals is likely to produce a more "dense" list of, say, counts.

      Anyone looking to use this strategy rather than looking up on the fly should benchmark well and update this documentation with what they learn.

      Specified by:
      globalOrdinalsMapping in class ValuesSource.Bytes.WithOrdinals