public Double getDistinctRowCount(Project rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
ImmutableBitSet.Builder baseCols = ImmutableBitSet.builder();
ImmutableBitSet.Builder projCols = ImmutableBitSet.builder();
List<RexNode> projExprs = rel.getProjects();
RelMdUtil.splitCols(projExprs, groupKey, baseCols, projCols);
List<RexNode> notPushable = new ArrayList<RexNode>();
List<RexNode> pushable = new ArrayList<RexNode>();
RelOptUtil.splitFilters(
ImmutableBitSet.range(rel.getRowType().getFieldCount()), predicate, pushable, notPushable);
final RexBuilder rexBuilder = rel.getCluster().getRexBuilder();
// get the distinct row count of the child input, passing in the
// columns and filters that only reference the child; convert the
// filter to reference the children projection expressions
RexNode childPred = RexUtil.composeConjunction(rexBuilder, pushable, true);
RexNode modifiedPred;
if (childPred == null) {
modifiedPred = null;
} else {
modifiedPred = RelOptUtil.pushPastProject(childPred, rel);
}
Double distinctRowCount =
RelMetadataQuery.getDistinctRowCount(rel.getInput(), baseCols.build(), modifiedPred);
if (distinctRowCount == null) {
return null;
} else if (!notPushable.isEmpty()) {
RexNode preds = RexUtil.composeConjunction(rexBuilder, notPushable, true);
distinctRowCount *= RelMdUtil.guessSelectivity(preds);
}
// No further computation required if the projection expressions
// are all column references
if (projCols.cardinality() == 0) {
return distinctRowCount;
}
// multiply by the cardinality of the non-child projection expressions
for (int bit : projCols.build()) {
Double subRowCount = RelMdUtil.cardOfProjExpr(rel, projExprs.get(bit));
if (subRowCount == null) {
return null;
}
distinctRowCount *= subRowCount;
}
return RelMdUtil.numDistinctVals(distinctRowCount, RelMetadataQuery.getRowCount(rel));
}
public Double getDistinctRowCount(Values rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
Double selectivity = RelMdUtil.guessSelectivity(predicate);
// assume half the rows are duplicates
Double nRows = rel.getRows() / 2;
return RelMdUtil.numDistinctVals(nRows, nRows * selectivity);
}