kgyrtkirk commented on a change in pull request #1439:
URL: https://github.com/apache/hive/pull/1439#discussion_r487114620
##########
File path:
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveAggregateJoinTransposeRule.java
##########
@@ -303,6 +305,90 @@ public void onMatch(RelOptRuleCall call) {
}
}
+ /**
+ * Determines weather the give grouping is unique.
+ *
+ * Consider a join which might produce non-unique rows; but later the
results are aggregated again.
+ * This method determines if there are sufficient columns in the grouping
which have been present previously as unique column(s).
+ */
+ private boolean isGroupingUnique(RelNode input, ImmutableBitSet groups) {
+ if (groups.isEmpty()) {
+ return false;
+ }
+ RelMetadataQuery mq = input.getCluster().getMetadataQuery();
+ Set<ImmutableBitSet> uKeys = mq.getUniqueKeys(input);
+ for (ImmutableBitSet u : uKeys) {
+ if (groups.contains(u)) {
+ return true;
+ }
+ }
+ if (input instanceof Join) {
+ Join join = (Join) input;
+ RexBuilder rexBuilder = input.getCluster().getRexBuilder();
+ SimpleConditionInfo cond = new SimpleConditionInfo(join.getCondition(),
rexBuilder);
+
+ if (cond.valid) {
+ ImmutableBitSet newGroup =
groups.intersect(ImmutableBitSet.fromBitSet(cond.fields));
+ RelNode l = join.getLeft();
+ RelNode r = join.getRight();
+
+ int joinFieldCount = join.getRowType().getFieldCount();
+ int lFieldCount = l.getRowType().getFieldCount();
+
+ ImmutableBitSet groupL = newGroup.get(0, lFieldCount);
+ ImmutableBitSet groupR = newGroup.get(lFieldCount,
joinFieldCount).shift(-lFieldCount);
+
+ if (isGroupingUnique(l, groupL)) {
Review comment:
That could be done; and I'm sure it was true in this - but this logic
will work better if it could walk down as many joins as it could - we might
have an aggregate on top in the meantime a bunch of joins under it...so I feel
that it will be beneficial to retain it.
I feeled tempted to write a RelMd handler - however I don't think I could
just introduce a new one easily.
RelShuttle doesn't look like a good match - I'll leave it as a set of
`instanceof` calls for now.
I'll upload a new patch to see if digging deeper in the tree could do more
or not.
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