morrySnow commented on code in PR #17355:
URL: https://github.com/apache/doris/pull/17355#discussion_r1126263751
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/PushdownLimit.java:
##########
@@ -67,65 +74,45 @@ public List<Rule> buildRules() {
LogicalUnion union = limit.child();
ImmutableList<Plan> newUnionChildren =
union.children()
.stream()
- .map(child -> addLimit(limit, child))
+ .map(child -> limit.withChildren(child))
.collect(ImmutableList.toImmutableList());
+ if (union.children().equals(newUnionChildren)) {
+ return null;
+ }
return
limit.withChildren(union.withChildren(newUnionChildren));
})
- .toRule(RuleType.PUSH_LIMIT_THROUGH_UNION)
+ .toRule(RuleType.PUSH_LIMIT_THROUGH_UNION),
+ logicalLimit(logicalOneRowRelation())
+ .then(limit -> limit.getLimit() > 0
+ ? limit.child() : new
LogicalEmptyRelation(limit.child().getOutput()))
+ .toRule(RuleType.PUSH_LIMIT_THROUGH_ONE_ROW_RELATION),
Review Comment:
this rule name is not good. it do not push limit **THROUGH** one row relation
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/PushdownLimit.java:
##########
@@ -67,65 +74,45 @@ public List<Rule> buildRules() {
LogicalUnion union = limit.child();
ImmutableList<Plan> newUnionChildren =
union.children()
.stream()
- .map(child -> addLimit(limit, child))
+ .map(child -> limit.withChildren(child))
.collect(ImmutableList.toImmutableList());
+ if (union.children().equals(newUnionChildren)) {
+ return null;
+ }
return
limit.withChildren(union.withChildren(newUnionChildren));
})
- .toRule(RuleType.PUSH_LIMIT_THROUGH_UNION)
+ .toRule(RuleType.PUSH_LIMIT_THROUGH_UNION),
+ logicalLimit(logicalOneRowRelation())
+ .then(limit -> limit.getLimit() > 0
+ ? limit.child() : new
LogicalEmptyRelation(limit.child().getOutput()))
+ .toRule(RuleType.PUSH_LIMIT_THROUGH_ONE_ROW_RELATION),
+ logicalLimit(logicalEmptyRelation())
+ .then(UnaryNode::child)
+ .toRule(RuleType.PUSH_LIMIT_THROUGH_EMPTY_RELATION),
Review Comment:
ditto, may be eliminate limit on xxxx is better
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/PushdownLimit.java:
##########
@@ -40,24 +39,32 @@
* <p>
* Limit can't be push down if it has a valid offset info.
*/
-public class LimitPushDown implements RewriteRuleFactory {
+public class PushdownLimit implements RewriteRuleFactory {
@Override
public List<Rule> buildRules() {
return ImmutableList.of(
// limit -> join
logicalLimit(logicalJoin(any(),
any())).whenNot(Limit::hasValidOffset)
Review Comment:
maybe do not need `join(any(), any())`? `join()` is enough
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