[Enhancement] support lower/upper constant fold

fe/fe-core/src/main/java/com/starrocks/sql/optimizer/rewrite/ScalarOperatorFunctions.java

@@ -1248,6 +1248,16 @@ public static ConstantOperator substring(ConstantOperator value, ConstantOperato
         return ConstantOperator.createVarchar(string.substring(beginIndex, endIndex));
     }
 
+    @ConstantFunction(name = "lower", argTypes = {VARCHAR}, returnType = VARCHAR)
+    public static ConstantOperator lower(ConstantOperator str) {
+        return ConstantOperator.createVarchar(StringUtils.lowerCase(str.getVarchar()));
+    }
+
+    @ConstantFunction(name = "upper", argTypes = {VARCHAR}, returnType = VARCHAR)
+    public static ConstantOperator upper(ConstantOperator str) {
+        return ConstantOperator.createVarchar(StringUtils.upperCase(str.getVarchar()));
+    }
+
     @ConstantFunction(name = "replace", argTypes = {VARCHAR, VARCHAR, VARCHAR}, returnType = VARCHAR)
     public static ConstantOperator replace(ConstantOperator value, ConstantOperator target,
                                            ConstantOperator replacement) {

fe/fe-core/src/test/java/com/starrocks/connector/parser/trino/TrinoQueryTest.java

@@ -1031,7 +1031,7 @@ public void testTrim() throws Exception {
         assertPlanContains(sql, "<slot 2> : trim('  abcd')");
 
         sql = "select trim(trailing 'ER' from upper('worker'));";
-        assertPlanContains(sql, "<slot 2> : rtrim(upper('worker'), 'ER')");
+        assertPlanContains(sql, "<slot 2> : rtrim('WORKER', 'ER')");
 
         sql = "select trim(trailing from '  abcd');";
         assertPlanContains(sql, "<slot 2> : rtrim('  abcd')");

fe/fe-core/src/test/java/com/starrocks/sql/optimizer/rewrite/ScalarOperatorFunctionsTest.java

@@ -1462,6 +1462,16 @@ public void testReplace() {
         ).getVarchar());
     }
 
+    @Test
+    public void testLowerUpper() {
+        assertEquals("aaa", ScalarOperatorFunctions.lower(
+                new ConstantOperator("AAA", Type.VARCHAR)
+        ).getVarchar());
+        assertEquals("AAA", ScalarOperatorFunctions.upper(
+                new ConstantOperator("aaa", Type.VARCHAR)
+        ).getVarchar());
+    }
+
     /*
     test cases are generated by the following SQL by capturing:
     1. leap year

fe/fe-core/src/test/java/com/starrocks/sql/plan/ConstantExpressionTest.java

@@ -491,7 +491,7 @@ public void testGetQueryDump() throws Exception {
 
             // Non-constant arguments.
             {
-                String sql = "SELECT get_query_dump(lower('select count(v1) from t0')) from t0";
+                String sql = "SELECT get_query_dump(rtrim('select count(v1) from t0')) from t0";
                 Assert.assertThrows("Meta function get_query_dump does not support non-constant arguments",
                         SemanticException.class, () -> getFragmentPlan(sql));
             }

fe/fe-core/src/test/java/com/starrocks/sql/plan/ExpressionTest.java

@@ -1583,7 +1583,7 @@ public void testConstantFoldInLikeFunction() throws Exception {
 
         String sql2 = "select ilike('AA', concat('a', 'A'))";
         String plan2 = getFragmentPlan(sql2);
-        assertContains(plan2, "<slot 2> : like(lower('AA'), lower('aA'))");
+        assertContains(plan2, "<slot 2> : like('aa', 'aa')");
     }
 
     @Test