Implement Space function push down pingcap#5113

dbms/src/Flash/Coprocessor/DAGUtils.cpp

@@ -654,7 +654,7 @@ const std::unordered_map<tipb::ScalarFuncSig, String> scalar_func_map({
     //{tipb::ScalarFuncSig::Right, "cast"},
     {tipb::ScalarFuncSig::RpadUTF8, "rpadUTF8"},
     {tipb::ScalarFuncSig::Rpad, "rpad"},
-    //{tipb::ScalarFuncSig::Space, "cast"},
+    {tipb::ScalarFuncSig::Space, "space"},
     {tipb::ScalarFuncSig::Strcmp, "strcmp"},
     {tipb::ScalarFuncSig::Substring2ArgsUTF8, "substringUTF8"},
     {tipb::ScalarFuncSig::Substring3ArgsUTF8, "substringUTF8"},

dbms/src/Functions/FunctionsString.cpp

@@ -4188,6 +4188,53 @@ class FunctionLength : public IFunction
 private:
 };
 
+class FunctionSpace : public IFunction
+{
+public:
+    static constexpr auto name = "space";
+    FunctionSpace() = default;
+
+    static FunctionPtr create(const Context & /*context*/)
+    {
+        return std::make_shared<FunctionSpace>();
+    }
+
+    std::string getName() const override { return name; }
+    size_t getNumberOfArguments() const override { return 1; }
+
+    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
+    {
+        if (arguments.size() != 1)
+            throw Exception(
+                fmt::format("Number of arguments for function {} doesn't match: passed {}, should be 1.", getName(), arguments.size()),
+                ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+
+        return std::make_shared<DataTypeString>();
+    }
+
+    void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) const override
+    {
+        const ColumnPtr c0_col = block.getByPosition(arguments[0]).column;
+
+        Field res_field;
+        const ColumnConst * column_space_num = checkAndGetColumn<ColumnConst>(c0_col.get());
+        Int64 space_num = 0;
+
+        if (column_space_num)
+        {
+            space_num = column_space_num->getInt(0);
+        }
+        auto col_res = ColumnString::create();
+        col_res->reserve(space_num);
+
+        std::string res_string(space_num, ' ');
+        col_res->insert(res_string);
+        block.getByPosition(result).column = std::move(col_res);
+    }
+
+private:
+};
+
 class FunctionPosition : public IFunction
 {
 public:

dbms/src/Functions/tests/gtest_strings_space.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 StringSpace : public DB::tests::FunctionTest
+{
+public:
+    static constexpr auto func_name = "space";
+
+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({"  ", "", "          "}),
+        executeFunction(
+            func_name,
+            toVec({2, 0, 10})
+            ));
+}
+CATCH
+
+// test NULL
+TEST_F(StringLength, nullTest)
+{
+    ASSERT_COLUMN_EQ(
+        toVec({"", {}}),
+        executeFunction(
+            func_name,
+            toVec({"", {}})));
+}
+
+} // namespace tests
+} // namespace DB

tests/fullstack-test/expr/space.test

@@ -0,0 +1,59 @@
+# 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), b int, c double);
+
+mysql> insert into test.t values('www.pingcap.com', 12345, 123.45);
+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 space(40) from test.t;
++------------------------------------------+
+| space(40)                                |
++------------------------------------------+
+|                                          |
+|                                          |
+|                                          |
++------------------------------------------+
+
+
+mysql> select space('') from test.t;
++-----------+
+| space('') |
++-----------+
+|           |
+|           |
+|           |
++-----------+
+
+mysql> select space(NULL) from test.t;
++-------------+
+| space(NULL) |
++-------------+
+| NULL        |
+| NULL        |
+| NULL        |
++-------------+
+
+mysql> explain select space(40) from test.t;
++---------------------------+---------+--------------+---------------+----------------------------------------------------+
+| id                        | estRows | task         | access object | operator info                                      |
++---------------------------+---------+--------------+---------------+----------------------------------------------------+
+| TableReader_9             | 3.00    | root         |               | data:ExchangeSender_8                              |
+| └─ExchangeSender_8        | 3.00    | mpp[tiflash] |               | ExchangeType: PassThrough                          |
+|   └─Projection_4          | 3.00    | mpp[tiflash] |               |                                         ->Column#3 |
+|     └─TableFullScan_7     | 3.00    | mpp[tiflash] | table:t       | keep order:false, stats:pseudo                     |
++---------------------------+---------+--------------+---------------+----------------------------------------------------+
+