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  package org.apache.beam.sdk.extensions.sql.impl.rel;
  
  import org.apache.beam.sdk.annotations.Internal;
  import org.apache.beam.sdk.extensions.sql.impl.planner.BeamCostModel;
  import org.apache.beam.sdk.extensions.sql.impl.planner.BeamRelMetadataQuery;
  import org.apache.beam.sdk.extensions.sql.impl.planner.NodeStats;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.plan.RelOptCluster;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.plan.RelOptPlanner;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.plan.RelTraitSet;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.RelNode;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.core.Calc;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rex.RexLocalRef;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rex.RexNode;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rex.RexProgram;
  
  /** BeamRelNode to replace {@code Project} and {@code Filter} node. */
  @Internal
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public abstract class AbstractBeamCalcRel extends Calc implements BeamRelNode {
  
    public AbstractBeamCalcRel(
        RelOptCluster cluster, RelTraitSet traits, RelNode input, RexProgram program) {
      super(cluster, traits, input, program);
    }
  
    public boolean isInputSortRelAndLimitOnly() {
      return (input instanceof BeamSortRel) && ((BeamSortRel) input).isLimitOnly();
    }
  
    public int getLimitCountOfSortRel() {
      if (input instanceof BeamSortRel) {
        return ((BeamSortRel) input).getCount();
      }
  
      throw new RuntimeException("Could not get the limit count from a non BeamSortRel input.");
    }
  
    @Override
    public boolean deepEquals(Object obj) {
      if (!super.deepEquals(obj) || !(obj instanceof AbstractBeamCalcRel)) {
        return false;
      }
      // Beam cares about output field names
      final AbstractBeamCalcRel other = (AbstractBeamCalcRel) obj;
      return this.getRowType().getFieldNames().equals(other.getRowType().getFieldNames());
    }
  
    @Override
    public NodeStats estimateNodeStats(BeamRelMetadataQuery mq) {
      NodeStats inputStat = BeamSqlRelUtils.getNodeStats(input, mq);
      double selectivity = estimateFilterSelectivity(getInput(), program, mq);
  
      return inputStat.multiply(selectivity);
    }
  
    private static double estimateFilterSelectivity(
        RelNode child, RexProgram program, RelMetadataQuery mq) {
      // Similar to calcite, if the calc node is representing filter operation we estimate the filter
      // selectivity based on the number of equality conditions, number of inequality conditions, ....
      RexLocalRef programCondition = program.getCondition();
      RexNode condition;
      if (programCondition == null) {
        condition = null;
      } else {
        condition = program.expandLocalRef(programCondition);
      }
      // Currently this gets the selectivity based on Calcite's Selectivity Handler (RelMdSelectivity)
      return mq.getSelectivity(child, condition);
    }
  
    @Override
    public BeamCostModel beamComputeSelfCost(RelOptPlanner planner, BeamRelMetadataQuery mq) {
      NodeStats inputStat = BeamSqlRelUtils.getNodeStats(this.input, mq);
      return BeamCostModel.FACTORY.makeCost(inputStat.getRowCount(), inputStat.getRate());
    }
  }
  