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[Improvement](Nereids) Restrict the condition to apply MergeConsecutiveLimits rule (#12624)

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This PR added a condition check for MergeConsecutiveLimits rule: the input upper limit should not have valid offset info.
This commit is contained in:
Shuo Wang
2022-09-16 13:05:39 +08:00
committed by GitHub
parent 0f6dbb5769
commit 131f2a42d2
2 changed files with 15 additions and 14 deletions
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27
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/MergeConsecutiveLimits.java
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@ -21,33 +21,34 @@ import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.rules.rewrite.OneRewriteRuleFactory;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.algebra.Limit;
import org.apache.doris.nereids.trees.plans.logical.LogicalLimit;
import java.util.List;
/**
* this rule aims to merge consecutive limits.
* LIMIT1(limit=10, offset=4)
* This rule aims to merge consecutive limits.
* <pre>
* input plan:
* LIMIT1(limit=10, offset=0)
* |
* LIMIT2(limit=3, offset=5)
*
* transformed to
* LIMITl(limit=3, offset=5)
* where
* LIMIT.limit = min(LIMIT1.limit, LIMIT2.limit)
* LIMIT.offset = LIMIT2.offset
* LIMIT1.offset is ignored
* output plan:
* LIMIT(limit=3, offset=5)
*
* merged limit = min(LIMIT1.limit, LIMIT2.limit)
* merged offset = LIMIT2.offset
* </pre>
* Note that the top limit should not have valid offset info.
*/
public class MergeConsecutiveLimits extends OneRewriteRuleFactory {
@Override
public Rule build() {
return logicalLimit(logicalLimit()).then(upperLimit -> {
return logicalLimit(logicalLimit()).whenNot(Limit::hasValidOffset).then(upperLimit -> {
LogicalLimit<? extends Plan> bottomLimit = upperLimit.child();
List<Plan> children = bottomLimit.children();
return new LogicalLimit<>(
Math.min(upperLimit.getLimit(), bottomLimit.getLimit()),
bottomLimit.getOffset(),
children.get(0)
bottomLimit.child()
);
}).toRule(RuleType.MERGE_CONSECUTIVE_LIMITS);
}

2
fe/fe-core/src/test/java/org/apache/doris/nereids/rules/rewrite/logical/MergeConsecutiveLimitsTest.java
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@ -34,7 +34,7 @@ public class MergeConsecutiveLimitsTest {
public void testMergeConsecutiveLimits() {
LogicalLimit limit3 = new LogicalLimit<>(3, 5, new UnboundRelation(Lists.newArrayList("db", "t")));
LogicalLimit limit2 = new LogicalLimit<>(2, 0, limit3);
LogicalLimit limit1 = new LogicalLimit<>(10, 2, limit2);
LogicalLimit limit1 = new LogicalLimit<>(10, 0, limit2);
CascadesContext context = MemoTestUtils.createCascadesContext(limit1);
List<Rule> rules = Lists.newArrayList(new MergeConsecutiveLimits().build());