public RelMetadataProvider getMetadataProvider() {
    return ChainedRelMetadataProvider.of(
               ImmutableList.of(
                   ReflectiveRelMetadataProvider.reflectiveSource(this,
                       BuiltInMethod.NON_CUMULATIVE_COST.method),
                   RelMdPercentageOriginalRows.SOURCE));
  }
HiveRelMdCost supplies the implementation of cost model.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/cost/HiveRelMdCost.java