[fix](Nereids) fix fold constant by be return type mismatched (#39723)

when using fold constant by be, the return type of substring('123456', 1, 3) would changed to be text, which we want it to be 3
apache · Oct 8, 2024 · 6dcdb03 · 6dcdb03
1 parent 21718c5
commit 6dcdb03
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diff --git a/...e/src/main/java/org/apache/doris/nereids/rules/expression/rules/FoldConstantRuleOnBE.java b/...e/src/main/java/org/apache/doris/nereids/rules/expression/rules/FoldConstantRuleOnBE.java
@@ -109,7 +109,16 @@ private Expression replace(Expression root, Map<String, Expression> constMap, Ma
             if (newChild != child) {
                 hasNewChildren = true;
             }
-            newChildren.add(newChild);
+            if (!newChild.getDataType().equals(child.getDataType())) {
+                try {
+                    newChildren.add(newChild.castTo(child.getDataType()));
+                } catch (Exception e) {
+                    LOG.warn("expression of type {} cast to {} failed. ", newChild.getDataType(), child.getDataType());
+                    newChildren.add(newChild);
+                }
+            } else {
+                newChildren.add(newChild);
+            }
         }
         return hasNewChildren ? root.withChildren(newChildren) : root;
     }

diff --git a/regression-test/suites/nereids_p0/expression/fold_constant/fold_constant_by_be.groovy b/regression-test/suites/nereids_p0/expression/fold_constant/fold_constant_by_be.groovy
@@ -40,4 +40,9 @@ suite("fold_constant_by_be") {
     sql """ INSERT INTO str_tb VALUES (2, repeat("test1111", 10000)); """
 
     qt_sql_1 """ select length(v1) from str_tb; """
-}
+
+    explain {
+        sql("verbose select substring('123456', 1, 3)")
+        contains "varchar(3)"
+    }
+}