org.apache.drill.exec.planner.cost.DrillRelMdDistinctRowCount Maven / Gradle / Ivy

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package org.apache.drill.exec.planner.cost;

import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.metadata.ReflectiveRelMetadataProvider;
import org.apache.calcite.rel.metadata.RelMdDistinctRowCount;
import org.apache.calcite.rel.metadata.RelMetadataProvider;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.util.BuiltInMethod;
import org.apache.calcite.util.ImmutableBitSet;
import org.apache.drill.exec.planner.logical.DrillScanRel;

public class DrillRelMdDistinctRowCount extends RelMdDistinctRowCount{
  private static final DrillRelMdDistinctRowCount INSTANCE =
      new DrillRelMdDistinctRowCount();

  public static final RelMetadataProvider SOURCE =
      ReflectiveRelMetadataProvider.reflectiveSource(
          BuiltInMethod.DISTINCT_ROW_COUNT.method, INSTANCE);

  @Override
  public Double getDistinctRowCount(RelNode rel, ImmutableBitSet groupKey, RexNode predicate) {
    if (rel instanceof DrillScanRel) {
      return getDistinctRowCount((DrillScanRel) rel, groupKey, predicate);
    } else {
      return super.getDistinctRowCount(rel, groupKey, predicate);
    }
  }

  private Double getDistinctRowCount(DrillScanRel scan, ImmutableBitSet groupKey, RexNode predicate) {
    // Consistent with the estimation of Aggregate row count in RelMdRowCount : distinctRowCount = rowCount * 10%.
    return scan.getRows() * 0.1;
  }

}