How to use

RelMdDistinctRowCount

in

org.apache.calcite.rel.metadata

@Override
public Double getDistinctRowCount(RelNode rel, RelMetadataQuery mq, ImmutableBitSet groupKey,
  RexNode predicate) {
 if (rel instanceof HiveTableScan) {
  return getDistinctRowCount((HiveTableScan) rel, mq, groupKey, predicate);
 }
 /*
  * For now use Calcite' default formulas for propagating NDVs up the Query
  * Tree.
  */
 return super.getDistinctRowCount(rel, mq, groupKey, predicate);
}

@Override
public Double getDistinctRowCount(RelNode rel, RelMetadataQuery mq, ImmutableBitSet groupKey,
  RexNode predicate) {
 if (rel instanceof HiveTableScan) {
  return getDistinctRowCount((HiveTableScan) rel, mq, groupKey, predicate);
 }
 /*
  * For now use Calcite' default formulas for propagating NDVs up the Query
  * Tree.
  */
 return super.getDistinctRowCount(rel, mq, groupKey, predicate);
}

@Override
public Double getDistinctRowCount(RelNode rel, ImmutableBitSet groupKey,
  RexNode predicate) {
 if (rel instanceof HiveTableScan) {
  return getDistinctRowCount((HiveTableScan) rel, groupKey, predicate);
 }
 /*
  * For now use Calcite' default formulas for propagating NDVs up the Query
  * Tree.
  */
 return super.getDistinctRowCount(rel, groupKey, predicate);
}

 public Double getDistinctRowCount(RelSubset rel, RelMetadataQuery mq,
   ImmutableBitSet groupKey, RexNode predicate) {
  final RelNode best = rel.getBest();
  if (best != null) {
   return mq.getDistinctRowCount(best, groupKey, predicate);
  }
  if (!Bug.CALCITE_1048_FIXED) {
   return getDistinctRowCount((RelNode) rel, mq, groupKey, predicate);
  }
  Double d = null;
  for (RelNode r2 : rel.getRels()) {
   try {
    Double d2 = mq.getDistinctRowCount(r2, groupKey, predicate);
    d = NumberUtil.min(d, d2);
   } catch (CyclicMetadataException e) {
    // Ignore this relational expression; there will be non-cyclic ones
    // in this set.
   }
  }
  return d;
 }
}

 public Double getDistinctRowCount(RelSubset rel, RelMetadataQuery mq,
   ImmutableBitSet groupKey, RexNode predicate) {
  final RelNode best = rel.getBest();
  if (best != null) {
   return mq.getDistinctRowCount(best, groupKey, predicate);
  }
  if (!Bug.CALCITE_1048_FIXED) {
   return getDistinctRowCount((RelNode) rel, mq, groupKey, predicate);
  }
  Double d = null;
  for (RelNode r2 : rel.getRels()) {
   try {
    Double d2 = mq.getDistinctRowCount(r2, groupKey, predicate);
    d = NumberUtil.min(d, d2);
   } catch (CyclicMetadataException e) {
    // Ignore this relational expression; there will be non-cyclic ones
    // in this set.
   }
  }
  return d;
 }
}