Kikyou1997 commented on code in PR #12274:
URL: https://github.com/apache/doris/pull/12274#discussion_r962339380
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fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/PruneAggChildColumns.java:
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@@ -54,15 +59,65 @@ public class PruneAggChildColumns extends
OneRewriteRuleFactory {
@Override
public Rule build() {
return
RuleType.COLUMN_PRUNE_AGGREGATION_CHILD.build(logicalAggregate().then(agg -> {
+ Slot slot = handleAggregateConstant(agg);
+ List<Slot> childOutput = agg.child().getOutput();
+ if (slot != null) {
+ if (childOutput.size() == 1 &&
childOutput.get(0).equals(slot)) {
+ return agg;
+ }
+ return agg.withChildren(ImmutableList.of(new
LogicalProject<>(ImmutableList.of(slot), agg.child())));
+ }
List<Expression> slots = Lists.newArrayList();
slots.addAll(agg.getExpressions());
Set<Slot> outputs = SlotExtractor.extractSlot(slots);
- List<NamedExpression> prunedOutputs =
agg.child().getOutput().stream().filter(outputs::contains)
+ List<NamedExpression> prunedOutputs =
childOutput.stream().filter(outputs::contains)
.collect(Collectors.toList());
if (prunedOutputs.size() == agg.child().getOutput().size()) {
return agg;
}
return agg.withChildren(ImmutableList.of(new
LogicalProject<>(prunedOutputs, agg.child())));
}));
}
+
+ /**
+ * For these aggregate function with constant param. Such as:
+ * count(*), count(1), sum(1)..etc.
+ * @return null, if there exists an aggregation function that its
parameters contains non-constant expr.
+ * else return a slot with min data type.
+ */
+ private Slot handleAggregateConstant(LogicalAggregate<GroupPlan> agg) {
+ List<NamedExpression> outputExpressions = agg.getOutputExpressions();
+ for (NamedExpression namedExpression : outputExpressions) {
+ if (!(namedExpression instanceof Alias)) {
+ return null;
+ }
+ Expression childOfAlias = ((Alias) namedExpression).child();
+ if (!(childOfAlias instanceof AggregateFunction)) {
+ return null;
+ }
+ if (childOfAlias instanceof Count) {
+ Count countFunc = (Count) childOfAlias;
+ if (!countFunc.isStar()) {
+ return null;
+ }
+ } else if (childOfAlias.children().stream().anyMatch(e ->
!e.isConstant())) {
Review Comment:
Just can't get it...could you give a sample case pls ? We could only pass a
scalar function or a function that returns a constant value like `NOW()` as the
params of agg function, for the former, this rule is useless , for the latter,
it should be cast to literal before this rule, so what's the meaning of
`generate random output`?
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