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);
}
}
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);
}
public Double getDistinctRowCount(Join rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
return RelMdUtil.getJoinDistinctRowCount(rel, rel.getJoinType(), groupKey, predicate, false);
}
public Double getDistinctRowCount(Filter rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
// REVIEW zfong 4/18/06 - In the Broadbase code, duplicates are not
// removed from the two filter lists. However, the code below is
// doing so.
RexNode unionPreds =
RelMdUtil.unionPreds(rel.getCluster().getRexBuilder(), predicate, rel.getCondition());
return RelMetadataQuery.getDistinctRowCount(rel.getInput(), groupKey, unionPreds);
}
// Catch-all rule when none of the others apply.
public Double getDistinctRowCount(RelNode rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
// REVIEW zfong 4/19/06 - Broadbase code does not take into
// consideration selectivity of predicates passed in. Also, they
// assume the rows are unique even if the table is not
boolean uniq = RelMdUtil.areColumnsDefinitelyUnique(rel, groupKey);
if (uniq) {
return NumberUtil.multiply(
RelMetadataQuery.getRowCount(rel), RelMetadataQuery.getSelectivity(rel, predicate));
}
return null;
}
public Double getDistinctRowCount(SemiJoin rel, ImmutableBitSet groupKey, RexNode predicate) {
if (predicate == null || predicate.isAlwaysTrue()) {
if (groupKey.isEmpty()) {
return 1D;
}
}
// create a RexNode representing the selectivity of the
// semijoin filter and pass it to getDistinctRowCount
RexNode newPred = RelMdUtil.makeSemiJoinSelectivityRexNode(rel);
if (predicate != null) {
RexBuilder rexBuilder = rel.getCluster().getRexBuilder();
newPred = rexBuilder.makeCall(SqlStdOperatorTable.AND, newPred, predicate);
}
return RelMetadataQuery.getDistinctRowCount(rel.getLeft(), groupKey, newPred);
}
public void onMatch(RelOptRuleCall call) {
AggregateRel aggRel = call.rel(0);
UnionRel unionRel = call.rel(1);
if (!unionRel.all) {
// This transformation is only valid for UNION ALL.
// Consider t1(i) with rows (5), (5) and t2(i) with
// rows (5), (10), and the query
// select sum(i) from (select i from t1) union (select i from t2).
// The correct answer is 15. If we apply the transformation,
// we get
// select sum(i) from
// (select sum(i) as i from t1) union (select sum(i) as i from t2)
// which yields 25 (incorrect).
return;
}
RelOptCluster cluster = unionRel.getCluster();
List<AggregateCall> transformedAggCalls =
transformAggCalls(
aggRel.getCluster().getTypeFactory(),
aggRel.getGroupSet().cardinality(),
aggRel.getAggCallList());
if (transformedAggCalls == null) {
// we've detected the presence of something like AVG,
// which we can't handle
return;
}
boolean anyTransformed = false;
// create corresponding aggs on top of each union child
List<RelNode> newUnionInputs = new ArrayList<RelNode>();
for (RelNode input : unionRel.getInputs()) {
boolean alreadyUnique = RelMdUtil.areColumnsDefinitelyUnique(input, aggRel.getGroupSet());
if (alreadyUnique) {
newUnionInputs.add(input);
} else {
anyTransformed = true;
newUnionInputs.add(
new AggregateRel(cluster, input, aggRel.getGroupSet(), aggRel.getAggCallList()));
}
}
if (!anyTransformed) {
// none of the children could benefit from the pushdown,
// so bail out (preventing the infinite loop to which most
// planners would succumb)
return;
}
// create a new union whose children are the aggs created above
UnionRel newUnionRel = new UnionRel(cluster, newUnionInputs, true);
AggregateRel newTopAggRel =
new AggregateRel(cluster, newUnionRel, aggRel.getGroupSet(), transformedAggCalls);
// In case we transformed any COUNT (which is always NOT NULL)
// to SUM (which is always NULLABLE), cast back to keep the
// planner happy.
RelNode castRel = RelOptUtil.createCastRel(newTopAggRel, aggRel.getRowType(), false);
call.transformTo(castRel);
}
