asolimando commented on code in PR #4494:
URL: https://github.com/apache/calcite/pull/4494#discussion_r2259794264
##########
core/src/main/java/org/apache/calcite/rel/rules/IntersectToDistinctRule.java:
##########
@@ -126,12 +143,86 @@ public IntersectToDistinctRule(Class<? extends Intersect>
intersectClass,
call.transformTo(relBuilder.build());
}
+ /**
+ * Variant performing a partial aggregation pushdown.
+ *
+ * <p>Original query:
+ * <pre>{@code
+ * SELECT job FROM "scott".emp WHERE deptno = 10
+ * INTERSECT
+ * SELECT job FROM "scott".emp WHERE deptno = 20
+ * }</pre>
+ *
+ * <p>Query after conversion:
+ * <pre>{@code
+ * SELECT job
+ * FROM (
+ * SELECT job, SUM(c)
+ * FROM (
+ * SELECT job, COUNT(*) AS c FROM "scott".emp
+ * WHERE deptno = 10 GROUP BY job
+ * UNION ALL
+ * SELECT job, COUNT(*) AS c FROM "scott".emp
+ * WHERE deptno = 20 GROUP BY job)
+ * GROUP BY job)
+ * WHERE c = 2
+ * }</pre>
+ */
+ public void onMatchAggregatePushdown(RelOptRuleCall call) {
+ final Intersect intersect = call.rel(0);
+ if (intersect.all) {
+ return; // nothing we can do
+ }
+ final RelOptCluster cluster = intersect.getCluster();
+ final RexBuilder rexBuilder = cluster.getRexBuilder();
+ final RelBuilder relBuilder = call.builder();
+
+ // 1st level aggregate: create an aggregate(col0, col1, count() as c) for
each branch
+ for (RelNode input : intersect.getInputs()) {
+ relBuilder.push(input);
+ relBuilder.aggregate(relBuilder.groupKey(relBuilder.fields()),
+ relBuilder.countStar(null));
Review Comment:
I haven't re-checked the logic of the original rule as it's out of scope for
the current PR (removing the plan regression introduced by CALCITE-6893), so
it's possible that there are further improvements that can be made, but this
should be discussed in a new, dedicated ticket.
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