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

/*
 * 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 <DataTypes/DataTypeString.h>
#include <Parser/FunctionParser.h>

namespace DB
{
namespace ErrorCodes
{
    extern const int BAD_ARGUMENTS;
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
}
}

namespace local_engine
{

class FunctionParserDecode : public FunctionParser
{
public:
    explicit FunctionParserDecode(ParserContextPtr parser_context_) : FunctionParser(parser_context_) { }
    ~FunctionParserDecode() override = default;

    static constexpr auto name = "decode";

    String getName() const override { return name; }

    const DB::ActionsDAG::Node * parse(
        const substrait::Expression_ScalarFunction & substrait_func,
        DB::ActionsDAG & actions_dag) const override
    {
        /// Parse decode(bin, charset) as convertCharset(bin, charset, 'UTF-8')
        auto parsed_args = parseFunctionArguments(substrait_func, actions_dag);
        if (parsed_args.size() != 2)
            throw DB::Exception(DB::ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH, "Function {} requires exactly two arguments", getName());

        const auto * bin_arg = parsed_args[0];
        const auto * from_charset_arg = parsed_args[1];
        const auto * to_charset_arg = addColumnToActionsDAG(actions_dag, std::make_shared<DB::DataTypeString>(), "UTF-8");
        const auto * result_node = toFunctionNode(actions_dag, "convertCharset", {bin_arg, from_charset_arg, to_charset_arg});
        return convertNodeTypeIfNeeded(substrait_func, result_node, actions_dag);
    }
};

static FunctionParserRegister<FunctionParserDecode> register_decode;
}