add new file

cpp-ch/local-engine/Parser/scalar_function_parser/chr.cpp

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+/*
+ * 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.
+ */
+#include <Parser/FunctionParser.h>
+#include <DataTypes/IDataType.h>
+#include <Common/CHUtil.h>
+#include <Core/Field.h>
+
+namespace DB
+{
+namespace ErrorCodes
+{
+    extern const int BAD_ARGUMENTS;
+    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
+}
+}
+
+namespace local_engine
+{
+class FunctionParserChr : public FunctionParser
+{
+public:
+    explicit FunctionParserChr(SerializedPlanParser * plan_parser_) : FunctionParser(plan_parser_) { }
+    ~FunctionParserChr() override = default;
+    static constexpr auto name = "chr";
+    String getName() const override { return name; }
+
+    const ActionsDAG::Node * parse(
+    const substrait::Expression_ScalarFunction & substrait_func,
+    ActionsDAGPtr & actions_dag) const override
+    {
+        auto parsed_args = parseFunctionArguments(substrait_func, "", actions_dag);
+        if (parsed_args.size() != 1)
+            throw Exception(DB::ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH, "Function {} requires two or three arguments", getName());
+
+        /*
+            parse chr(number) as if(number < 0, '', char(0, number), 'unicode', 'utf-8'))
+        */
+        const auto & num_arg = parsed_args[0];
+        const auto * const_zero_node = addColumnToActionsDAG(actions_dag, std::make_shared<DataTypeInt32>(), 0);
+        const auto * const_empty_node = addColumnToActionsDAG(actions_dag, std::make_shared<DataTypeString>(), "");
+        const auto * const_four_node = addColumnToActionsDAG(actions_dag, std::make_shared<DataTypeInt32>(), 4);
+        const auto * const_unicode_node = addColumnToActionsDAG(actions_dag, std::make_shared<DataTypeString>(), "unicode");
+        const auto * const_utf8_node = addColumnToActionsDAG(actions_dag, std::make_shared<DataTypeString>(), "utf-8");
+
+        const auto * less_node = toFunctionNode(actions_dag, "less", {num_arg, const_zero_node});
+
+        const auto * char_node = toFunctionNode(actions_dag, "char", {const_zero_node, num_arg});
+        const auto * convert_charset_node = toFunctionNode(actions_dag, "convertCharset", {char_node, const_unicode_node, const_utf8_node});
+
+        const auto * if_node = toFunctionNode(actions_dag, "if", {less_node, const_empty_node, convert_charset_node});
+        const auto * result_node = convertNodeTypeIfNeeded(substrait_func, if_node, actions_dag);
+        return result_node;
+    }
+};
+
+static FunctionParserRegister<FunctionParserChr> register_chr;
+}