How to use

linear

method

in

org.apache.calcite.rel.metadata.RelMdUtil

private double getIntervalCostMultiplier() {
  int days = 0;
  for (Interval interval : intervals) {
    days += interval.toDuration().getStandardDays();
  }
  // Cost increases with the wider interval being queries.
  // A plan querying 10 or more years of data will have 10x the cost of a
  // plan returning 1 day data.
  // A plan where least interval is queries will be preferred.
  return RelMdUtil.linear(days, 1, DAYS_IN_TEN_YEARS, 0.1d, 1d);
}

private double getIntervalCostMultiplier() {
 int days = 0;
 for (Interval interval : intervals) {
  days += interval.toDuration().getStandardDays();
 }
 // Cost increases with the wider interval being queries.
 // A plan querying 10 or more years of data will have 10x the cost of a
 // plan returning 1 day data.
 // A plan where least interval is queries will be preferred.
 return RelMdUtil.linear(days, 1, DAYS_IN_TEN_YEARS, 0.1d, 1d);
}

/** Unit test for {@link RelMdUtil#linear(int, int, int, double, double)}. */
@Test public void testLinear() {
 assertThat(RelMdUtil.linear(0, 0, 10, 100, 200), is(100d));
 assertThat(RelMdUtil.linear(5, 0, 10, 100, 200), is(150d));
 assertThat(RelMdUtil.linear(6, 0, 10, 100, 200), is(160d));
 assertThat(RelMdUtil.linear(10, 0, 10, 100, 200), is(200d));
 assertThat(RelMdUtil.linear(-2, 0, 10, 100, 200), is(100d));
 assertThat(RelMdUtil.linear(12, 0, 10, 100, 200), is(200d));
}

/** Unit test for {@link RelMdUtil#linear(int, int, int, double, double)}. */
@Test public void testLinear() {
 assertThat(RelMdUtil.linear(0, 0, 10, 100, 200), is(100d));
 assertThat(RelMdUtil.linear(5, 0, 10, 100, 200), is(150d));
 assertThat(RelMdUtil.linear(6, 0, 10, 100, 200), is(160d));
 assertThat(RelMdUtil.linear(10, 0, 10, 100, 200), is(200d));
 assertThat(RelMdUtil.linear(-2, 0, 10, 100, 200), is(100d));
 assertThat(RelMdUtil.linear(12, 0, 10, 100, 200), is(200d));
}

@Override public RelOptCost computeSelfCost(RelOptPlanner planner,
  RelMetadataQuery mq) {
 return Util.last(rels)
   .computeSelfCost(planner, mq)
   // Cost increases with the number of fields queried.
   // A plan returning 100 or more columns will have 2x the cost of a
   // plan returning 2 columns.
   // A plan where all extra columns are pruned will be preferred.
   .multiplyBy(
     RelMdUtil.linear(querySpec.fieldNames.size(), 2, 100, 1d, 2d))
   .multiplyBy(getQueryTypeCostMultiplier())
   // A Scan leaf filter is better than having filter spec if possible.
   .multiplyBy(rels.size() > 1 && rels.get(1) instanceof Filter ? 0.5 : 1.0)
   // a plan with sort pushed to druid is better than doing sort outside of druid
   .multiplyBy(Util.last(rels) instanceof Sort ? 0.1 : 1.0)
   .multiplyBy(getIntervalCostMultiplier());
}

@Override public RelOptCost computeSelfCost(RelOptPlanner planner,
  RelMetadataQuery mq) {
  return Util.last(rels)
    .computeSelfCost(planner, mq)
    // Cost increases with the number of fields queried.
    // A plan returning 100 or more columns will have 2x the cost of a
    // plan returning 2 columns.
    // A plan where all extra columns are pruned will be preferred.
    .multiplyBy(
      RelMdUtil.linear(querySpec.fieldNames.size(), 2, 100, 1d, 2d))
    .multiplyBy(getQueryTypeCostMultiplier())
    // a plan with sort pushed to druid is better than doing sort outside of druid
    .multiplyBy(Util.last(rels) instanceof Sort ? 0.1 : 1.0)
    .multiplyBy(getIntervalCostMultiplier());
}