Implement ReverseUTF8/Reverse function push down pingcap#5111

dbms/src/Flash/Coprocessor/DAGUtils.cpp

@@ -648,8 +648,8 @@ const std::unordered_map<tipb::ScalarFuncSig, String> scalar_func_map({
     //{tipb::ScalarFuncSig::Quote, "cast"},
     //{tipb::ScalarFuncSig::Repeat, "cast"},
     {tipb::ScalarFuncSig::Replace, "replaceAll"},
-    //{tipb::ScalarFuncSig::ReverseUTF8, "cast"},
-    //{tipb::ScalarFuncSig::Reverse, "cast"},
+    {tipb::ScalarFuncSig::ReverseUTF8, "reverseUTF8"},
+    {tipb::ScalarFuncSig::Reverse, "reverse"},
     {tipb::ScalarFuncSig::RightUTF8, "rightUTF8"},
     //{tipb::ScalarFuncSig::Right, "cast"},
     {tipb::ScalarFuncSig::RpadUTF8, "rpadUTF8"},

dbms/src/Functions/tests/gtest_strings_reverse.cpp

@@ -0,0 +1,74 @@
+// Copyright 2022 PingCAP, Ltd.
+//
+// Licensed 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.
+
+#include <Columns/ColumnString.h>
+#include <Columns/ColumnsNumber.h>
+#include <DataTypes/DataTypeNullable.h>
+#include <DataTypes/DataTypesNumber.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionsString.h>
+#include <Interpreters/Context.h>
+#include <TestUtils/FunctionTestUtils.h>
+#include <TestUtils/TiFlashTestBasic.h>
+
+#include <string>
+#include <vector>
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wsign-compare"
+#include <Poco/Types.h>
+
+#pragma GCC diagnostic pop
+
+namespace DB
+{
+namespace tests
+{
+class StringReverse : public DB::tests::FunctionTest
+{
+public:
+    static constexpr auto func_name = "reverse";
+protected:
+    ColumnWithTypeAndName toVec(const std::vector<std::optional<String>> & v)
+    {
+        return createColumn<Nullable<String>>(v);
+    }
+};
+
+// test string and string
+TEST_F(StringReverse, strAndStrTest)
+try
+{
+    ASSERT_COLUMN_EQ(
+        toVec({"olleh", "dlrow,olleh","", "pacgnip.www", "。。。试.测.文中"}),
+        executeFunction(
+            func_name,
+            toVec({"hello", "hello,world","", "www.pingcap", "中文.测.试。。。"}),
+            ));
+}
+CATCH
+
+// test NULL
+TEST_F(StringLength, nullTest)
+{
+    ASSERT_COLUMN_EQ(
+        toVec({"", {}}),
+        executeFunction(
+            func_name,
+            toVec({"", {}}),
+            ));
+}
+
+} // namespace tests
+} // namespace DB

tests/fullstack-test/expr/reverse.test

@@ -0,0 +1,49 @@
+# Copyright 2022 PingCAP, Ltd.
+#
+# Licensed 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.
+
+mysql> drop table if exists test.t;
+mysql> create table if not exists test.t(a char(20));
+
+mysql> insert into test.t values('hello');
+mysql> insert into test.t values('hello,world');
+mysql> insert into test.t values('');
+mysql> insert into test.t values('www.pingcap');
+mysql> insert into test.t values('中文.测.试。。。');
+mysql> alter table test.t set tiflash replica 1;
+func> wait_table test t
+
+mysql> set tidb_enforce_mpp=1; set tidb_isolation_read_engines='tiflash'; select reverse(a) from test.t;
++-------------------------+
+| reverse(a)              |
++-------------------------+
+| olleh                   |
+| dlrow,olleh             |
+|                         |
+| pacgnip.www             |
+| 。。。试.测.文中        |
++-------------------------+
+
+mysql> drop table if exists test.t;
+mysql> create table if not exists test.t(a char(20));
+mysql> insert into test.t values(NULL);
+
+func> wait_table test t
+mysql> set tidb_enforce_mpp=1; set tidb_isolation_read_engines='tiflash'; select reverse(a) from test.t;
++------------+
+| reverse(a) |
++------------+
+| NULL       |
++------------+
+
+