[GitHub] [doris] morrySnow commented on a diff in pull request #16114: [ehancement](nereids) Enhancement for limit clause.

[GitBox <gi...@apache.org>]

morrySnow commented on code in PR #16114:
URL: https://github.com/apache/doris/pull/16114#discussion_r1082166380


##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/logical/MergeLimits.java:
##########
@@ -43,11 +42,11 @@
 public class MergeLimits extends OneRewriteRuleFactory {
     @Override
     public Rule build() {
-        return logicalLimit(logicalLimit()).whenNot(Limit::hasValidOffset).then(upperLimit -> {
+        return logicalLimit(logicalLimit()).then(upperLimit -> {
             LogicalLimit<? extends Plan> bottomLimit = upperLimit.child();
             return new LogicalLimit<>(
                     Math.min(upperLimit.getLimit(), bottomLimit.getLimit()),
-                    bottomLimit.getOffset(),
+                    bottomLimit.getOffset() + upperLimit.getOffset(),
                     bottomLimit.child()

Review Comment:
   only sum offset is not right
   consider this scene:
   before merge:
   limit(limit = 7, offset = 5)
   +-- limit(limit = 10, offset = 5)
   
   after bottom limit, we get tuple from 6 to 15
   after top limit, we get tuple from 11 to 15
   
   so, after merge, we should get:
   limit(limit = 5, offset = 10)



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