How to use

computeSemiJoinSelectivity

method

in

org.apache.calcite.rel.metadata.RelMdUtil

/**
 * Computes the selectivity of a semijoin filter if it is applied on a fact
 * table. The computation is based on the selectivity of the dimension
 * table/columns and the number of distinct values in the fact table
 * columns.
 *
 * @param factRel fact table participating in the semijoin
 * @param dimRel  dimension table participating in the semijoin
 * @param rel     semijoin rel
 * @return calculated selectivity
 */
public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
  RelNode factRel, RelNode dimRel, SemiJoin rel) {
 return computeSemiJoinSelectivity(mq, factRel, dimRel, rel.getLeftKeys(),
   rel.getRightKeys());
}

/**
 * Computes the selectivity of a semijoin filter if it is applied on a fact
 * table. The computation is based on the selectivity of the dimension
 * table/columns and the number of distinct values in the fact table
 * columns.
 *
 * @param factRel fact table participating in the semijoin
 * @param dimRel  dimension table participating in the semijoin
 * @param rel     semijoin rel
 * @return calculated selectivity
 */
public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
  RelNode factRel, RelNode dimRel, SemiJoin rel) {
 return computeSemiJoinSelectivity(mq, factRel, dimRel, rel.getLeftKeys(),
   rel.getRightKeys());
}

/**
 * Computes the selectivity of a semijoin filter if it is applied on a fact
 * table. The computation is based on the selectivity of the dimension
 * table/columns and the number of distinct values in the fact table
 * columns.
 *
 * @param rel semijoin rel
 * @return calculated selectivity
 */
public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
  SemiJoin rel) {
 return computeSemiJoinSelectivity(mq, rel.getLeft(), rel.getRight(),
   rel.getLeftKeys(), rel.getRightKeys());
}

/**
 * Computes the selectivity of a semijoin filter if it is applied on a fact
 * table. The computation is based on the selectivity of the dimension
 * table/columns and the number of distinct values in the fact table
 * columns.
 *
 * @param rel semijoin rel
 * @return calculated selectivity
 */
public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
  SemiJoin rel) {
 return computeSemiJoinSelectivity(mq, rel.getLeft(), rel.getRight(),
   rel.getLeftKeys(), rel.getRightKeys());
}

/**
 * Creates a RexNode that stores a selectivity value corresponding to the
 * selectivity of a semijoin. This can be added to a filter to simulate the
 * effect of the semijoin during costing, but should never appear in a real
 * plan since it has no physical implementation.
 *
 * @param rel the semijoin of interest
 * @return constructed rexnode
 */
public static RexNode makeSemiJoinSelectivityRexNode(RelMetadataQuery mq,
  SemiJoin rel) {
 RexBuilder rexBuilder = rel.getCluster().getRexBuilder();
 double selectivity =
   computeSemiJoinSelectivity(mq, rel.getLeft(), rel.getRight(), rel);
 return rexBuilder.makeCall(ARTIFICIAL_SELECTIVITY_FUNC,
   rexBuilder.makeApproxLiteral(new BigDecimal(selectivity)));
}

/**
 * Creates a RexNode that stores a selectivity value corresponding to the
 * selectivity of a semijoin. This can be added to a filter to simulate the
 * effect of the semijoin during costing, but should never appear in a real
 * plan since it has no physical implementation.
 *
 * @param rel the semijoin of interest
 * @return constructed rexnode
 */
public static RexNode makeSemiJoinSelectivityRexNode(RelMetadataQuery mq,
  SemiJoin rel) {
 RexBuilder rexBuilder = rel.getCluster().getRexBuilder();
 double selectivity =
   computeSemiJoinSelectivity(mq, rel.getLeft(), rel.getRight(), rel);
 return rexBuilder.makeCall(ARTIFICIAL_SELECTIVITY_FUNC,
   rexBuilder.makeApproxLiteral(new BigDecimal(selectivity)));
}

  RelMdUtil.computeSemiJoinSelectivity(mq, factRel, dimRel, semiJoin);
if (selectivity > .5) {
 return 0;

  RelMdUtil.computeSemiJoinSelectivity(mq, factRel, dimRel, semiJoin);
if (selectivity > .5) {
 return 0;