Package org.apache.druid.segment

Class IdMapping.Builder

java.lang.Object
org.apache.druid.segment.IdMapping.Builder
Enclosing class:
IdMapping
public static class IdMapping.Builder extends Object

  • Method Details

    • ofCardinality

      public static IdMapping.Builder ofCardinality(int cardinality)
      Create a IdMapping where the cardinality is known, to use with addMapping(int) to simultaneously populate both forwardMapping and reverseMapping.

    • ofUnknownCardinality

      public static IdMapping.Builder ofUnknownCardinality()
      Create an IdMapping where the cardinality is not known up front. Since cardinality is unknown, reverseMapping is initialized to an empty array, and addForwardMapping(int) should be used to build the forwardMapping, when build() is called reverseMapping will be computed to produce the completed IdMapping. This is less efficient than ofCardinality(int), so it should be preferred if the value cardinality is in fact known

    • addMapping

      public void addMapping(int forwardId)
      Adds a lookup for the 'forwarded' index to the current highest index value, and a reverse lookup from this substitute index back to the original. This method can only be called when cardinality is known, to ensure that reverseMapping is initialized correctly.

    • addForwardMapping

      public void addForwardMapping(int forwardId)
      Adds a lookup for the 'forwarded' index to the current highest index value. This method can only be used when the cardinality is unknown, otherwise addMapping(int) should be used instead since the reverseMapping is only computed if knownCardinality is false

    • build

      public IdMapping build()