public void onMatch(RelOptRuleCall call) { UnionRel union = call.rel(0); if (union.all) { return; // nothing to do } UnionRel unionAll = new UnionRel(union.getCluster(), union.getInputs(), true); call.transformTo(RelOptUtil.createDistinctRel(unionAll)); }
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); }