[fix](planner)unnecessary cast will be added on children in CaseExpr sometimes

fe/fe-core/src/main/java/org/apache/doris/analysis/CaseExpr.java

@@ -235,25 +235,25 @@ public void analyzeImpl(Analyzer analyzer) throws AnalysisException {
         // Add casts to case expr to compatible type.
         if (hasCaseExpr) {
             // Cast case expr.
-            if (children.get(0).type != whenType) {
+            if (!children.get(0).getType().equals(whenType)) {
                 castChild(whenType, 0);
             }
             // Add casts to when exprs to compatible type.
             for (int i = loopStart; i < loopEnd; i += 2) {
-                if (children.get(i).type != whenType) {
+                if (!children.get(i).getType().equals(whenType)) {
                     castChild(whenType, i);
                 }
             }
         }
         // Cast then exprs to compatible type.
         for (int i = loopStart + 1; i < children.size(); i += 2) {
-            if (children.get(i).type != returnType) {
+            if (!children.get(i).getType().equals(returnType)) {
                 castChild(returnType, i);
             }
         }
         // Cast else expr to compatible type.
         if (hasElseExpr) {
-            if (children.get(children.size() - 1).type != returnType) {
+            if (!children.get(children.size() - 1).getType().equals(returnType)) {
                 castChild(returnType, children.size() - 1);
             }
         }

fe/fe-core/src/test/java/org/apache/doris/analysis/CaseExprTest.java

@@ -17,12 +17,16 @@
 
 package org.apache.doris.analysis;
 
+import org.apache.doris.catalog.PrimitiveType;
+import org.apache.doris.catalog.ScalarType;
+
 import com.clearspring.analytics.util.Lists;
 import mockit.Expectations;
 import mockit.Injectable;
 import org.junit.Assert;
 import org.junit.Test;
 
+import java.lang.reflect.Constructor;
 import java.util.List;
 
 public class CaseExprTest {
@@ -65,4 +69,44 @@ public void testIsNullable(@Injectable Expr caseExpr,
         };
         Assert.assertTrue(caseExpr3.isNullable());
     }
+
+    @Test
+    public void testTypeCast(
+            @Injectable Expr caseExpr,
+            @Injectable Expr whenExpr,
+            @Injectable Expr thenExpr,
+            @Injectable Expr elseExpr) throws Exception {
+        CaseWhenClause caseWhenClause = new CaseWhenClause(whenExpr, thenExpr);
+        List<CaseWhenClause> caseWhenClauseList = Lists.newArrayList();
+        caseWhenClauseList.add(caseWhenClause);
+        CaseExpr expr = new CaseExpr(caseExpr, caseWhenClauseList, elseExpr);
+        Class<?> clazz = Class.forName("org.apache.doris.catalog.ScalarType");
+        Constructor<?> constructor = clazz.getDeclaredConstructor(PrimitiveType.class);
+        constructor.setAccessible(true);
+        ScalarType intType = (ScalarType) constructor.newInstance(PrimitiveType.INT);
+        ScalarType tinyIntType = (ScalarType) constructor.newInstance(PrimitiveType.TINYINT);
+        new Expectations() {
+            {
+                caseExpr.getType();
+                result = intType;
+
+                whenExpr.getType();
+                result = ScalarType.createType(PrimitiveType.INT);
+                whenExpr.castTo(intType);
+                times = 0;
+
+                thenExpr.getType();
+                result = tinyIntType;
+                thenExpr.castTo(tinyIntType);
+                times = 0;
+
+                elseExpr.getType();
+                result = ScalarType.createType(PrimitiveType.TINYINT);
+                elseExpr.castTo(tinyIntType);
+                times = 0;
+            }
+        };
+        Analyzer analyzer = new Analyzer(null, null);
+        expr.analyzeImpl(analyzer);
+    }
 }

regression-test/data/correctness/test_case_when.out

@@ -3,3 +3,9 @@
 2	01	-1
 3	00	1
 
+-- !select_agg --
+1	90020004
+2	45010002
+3	90020004
+4	90020004
+

regression-test/suites/correctness/test_case_when.groovy

@@ -64,4 +64,16 @@ suite("test_case_when") {
             and channel_id = '00'
             group by hour_time, station_type; 
     """
-}
+
+    qt_select_agg """
+    SELECT
+      hour_time,
+      sum((CASE WHEN TRUE THEN merchant_id ELSE 0 END)) mid
+    FROM
+      dws_scan_qrcode_user_ts
+    GROUP BY
+      hour_time
+    ORDER BY
+      hour_time;
+    """
+}