cpp-ch/local-engine/Parser/scalar_function_parser/length.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/DataTypeNullable.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/IDataType.h>
#include <Parser/FunctionParser.h>

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

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

    static constexpr auto name = "char_length";

    String getName() const override { return name; }

    const DB::ActionsDAG::Node * parse(const substrait::Expression_ScalarFunction & substrait_func, DB::ActionsDAG & actions_dag) const override
    {
        /**
            parse length(a) as
                if input is binary type
                    length(a) as length(a)
                else
                    length(a) as char_length(a)
         */
        auto parsed_args = parseFunctionArguments(substrait_func, actions_dag);
        if (parsed_args.size() != 1)
            throw DB::Exception(DB::ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH, "Function {} requires exactly one arguments", getName());

        const auto * arg = parsed_args[0];
        const auto * new_arg = arg;
        if (isInt(removeNullable(arg->result_type)))
        {
            const auto * string_type_node = addColumnToActionsDAG(actions_dag, std::make_shared<DB::DataTypeString>(), "Nullable(String)");
            new_arg = toFunctionNode(actions_dag, "CAST", {arg, string_type_node});
        }

        auto optional_function_sigature = parser_context->getFunctionSignature(substrait_func);
        if (!optional_function_sigature)
            throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "Not found function {}", substrait_func.function_reference());
        auto function_signature = *optional_function_sigature;
        const DB::ActionsDAG::Node * result_node;
        if (function_signature.find("vbin") != std::string::npos)
            result_node = toFunctionNode(actions_dag, "length", {new_arg});
        else
            result_node = toFunctionNode(actions_dag, "char_length", {new_arg});

        return convertNodeTypeIfNeeded(substrait_func, result_node, actions_dag);
    }
};

static FunctionParserRegister<FunctionParserLength> register_length;
}