public Double getDistinctRowCount(Aggregate rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
// determine which predicates can be applied on the child of the
// aggregate
List<RexNode> notPushable = new ArrayList<RexNode>();
List<RexNode> pushable = new ArrayList<RexNode>();
RelOptUtil.splitFilters(rel.getGroupSet(), predicate, pushable, notPushable);
final RexBuilder rexBuilder = rel.getCluster().getRexBuilder();
RexNode childPreds = RexUtil.composeConjunction(rexBuilder, pushable, true);
// set the bits as they correspond to the child input
ImmutableBitSet.Builder childKey = ImmutableBitSet.builder();
RelMdUtil.setAggChildKeys(groupKey, rel, childKey);
Double distinctRowCount =
RelMetadataQuery.getDistinctRowCount(rel.getInput(), childKey.build(), childPreds);
if (distinctRowCount == null) {
return null;
} else if (notPushable.isEmpty()) {
return distinctRowCount;
} else {
RexNode preds = RexUtil.composeConjunction(rexBuilder, notPushable, true);
return distinctRowCount * RelMdUtil.guessSelectivity(preds);
}
}
