Add pipes_as_concat_mode (#2252)

This commit will add a new sql mode named MODE_PIPES_AS_CONCAT:
Description:
1、If this mode is active, '||' will be handled different from the original way ('||' and 'or' are seen as the same symbols in Doris) that it can be used to concat two exps and returns a new string. For example, 'a' || 'b' = 'ab' and 1 || 0 = '10'.
2. User can active this mode by "SET sql_mode = PIPES_AS_CONCAT", and deactive it by "SET sql_mode = '' ".

fe/src/test/java/org/apache/doris/analysis/SqlModeTest.java

@@ -0,0 +1,79 @@
+// 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.analysis;
+
+import org.apache.doris.qe.SqlModeHelper;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.StringReader;
+
+public class SqlModeTest {
+
+    @Test
+    public void testScannerConstructor() {
+        String stmt = new String("SELECT * FROM db1.tbl1 WHERE name = 'BILL GATES'");
+        SqlParser parser = new SqlParser(new SqlScanner(new StringReader(stmt)));
+        SelectStmt selectStmt = null;
+        try {
+            selectStmt = (SelectStmt) parser.parse().value;
+        } catch (Exception e) {
+            Assert.fail(e.getMessage());
+        }
+        Assert.assertEquals("SELECT  FROM `db1`.`tbl1` WHERE `name` = 'BILL GATES'", selectStmt.toSql());
+
+        parser = new SqlParser(new SqlScanner(new StringReader(stmt), SqlModeHelper.MODE_DEFAULT));
+        try {
+            selectStmt = (SelectStmt) parser.parse().value;
+        } catch (Exception e) {
+            Assert.fail(e.getMessage());
+        }
+        Assert.assertEquals("SELECT  FROM `db1`.`tbl1` WHERE `name` = 'BILL GATES'", selectStmt.toSql());
+    }
+
+    @Test
+    public void testPipesAsConcatMode() {
+        // Mode Active
+        String stmt = new String("SELECT 'a' || 'b' || 'c'");
+        SqlParser parser = new SqlParser(new SqlScanner(new StringReader(stmt), SqlModeHelper.MODE_PIPES_AS_CONCAT));
+        SelectStmt selectStmt = null;
+        try {
+            selectStmt = (SelectStmt) parser.parse().value;
+        } catch (Exception e) {
+            Assert.fail(e.getMessage());
+        }
+        Expr expr = selectStmt.getSelectList().getItems().get(0).getExpr();
+        if (!(expr instanceof FunctionCallExpr)) {
+            Assert.fail("Mode not working");
+        }
+        Assert.assertEquals("concat('a', 'b', 'c')", expr.toSql());
+
+        // Mode DeActive
+        parser = new SqlParser(new SqlScanner(new StringReader(stmt), SqlModeHelper.MODE_DEFAULT));
+        try {
+            selectStmt = (SelectStmt) parser.parse().value;
+        } catch (Exception e) {
+            Assert.fail(e.getMessage());
+        }
+        expr = selectStmt.getSelectList().getItems().get(0).getExpr();
+        if (!(expr instanceof CompoundPredicate)) {
+            Assert.fail();
+        }
+        Assert.assertEquals("(('a') OR ('b')) OR ('c')", expr.toSql());
+    }
+}