Modify mv rewrite rule on 'Count distinct' (#4382)

The rewrite rule named `CountToSum` does not distinguish between `Count` and `Count distinct` which causes `Count distinct` is rewritten as `Sum` incorrectly.
So this commit modified matching rule.
When the function is `Count distinct`, the rewrite rule will not take effect.

Fixed #4381

fe/fe-core/src/main/java/org/apache/doris/rewrite/mvrewrite/CountFieldToSum.java

@@ -60,6 +60,9 @@ public class CountFieldToSum implements ExprRewriteRule {
         if (fnExpr.getChildren().size() != 1 || !(fnExpr.getChild(0) instanceof SlotRef)) {
             return expr;
         }
+        if (fnExpr.getParams().isDistinct()) {
+            return expr;
+        }
         SlotRef fnChild0 = (SlotRef) fnExpr.getChild(0);
         Column column = fnChild0.getColumn();
         Table table = fnChild0.getTable();

fe/fe-core/src/test/java/org/apache/doris/rewrite/mvrewrite/CountFieldToSumTest.java

@@ -0,0 +1,69 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.apache.doris.rewrite.mvrewrite;
+
+import org.apache.doris.analysis.Analyzer;
+import org.apache.doris.analysis.Expr;
+import org.apache.doris.analysis.FunctionCallExpr;
+import org.apache.doris.analysis.SlotRef;
+import org.apache.doris.analysis.TableName;
+import org.apache.doris.catalog.FunctionSet;
+import org.apache.doris.common.AnalysisException;
+
+import com.google.common.collect.Lists;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.List;
+
+import mockit.Expectations;
+import mockit.Injectable;
+
+public class CountFieldToSumTest {
+
+    @Test
+    public void testCountDistinct(@Injectable Analyzer analyzer,
+                                  @Injectable FunctionCallExpr functionCallExpr) {
+        TableName tableName = new TableName("db1", "table1");
+        SlotRef slotRef = new SlotRef(tableName,"c1");
+        List<Expr>  params = Lists.newArrayList();
+        params.add(slotRef);
+
+        new Expectations() {
+            {
+                functionCallExpr.getFnName().getFunction();
+                result = FunctionSet.COUNT;
+                functionCallExpr.getChildren();
+                result = params;
+                functionCallExpr.getChild(0);
+                result = slotRef;
+                functionCallExpr.getParams().isDistinct();
+                result = true;
+            }
+        };
+        CountFieldToSum countFieldToSum = new CountFieldToSum();
+        try {
+            Expr rewrittenExpr = countFieldToSum.apply(functionCallExpr, analyzer);
+            Assert.assertTrue(rewrittenExpr instanceof FunctionCallExpr);
+            Assert.assertEquals(FunctionSet.COUNT, ((FunctionCallExpr) rewrittenExpr).getFnName().getFunction());
+        } catch (AnalysisException e) {
+            System.out.println(e.getMessage());
+        }
+    }
+}