ClickHouse

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#include <Functions/IFunction.h>
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#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionHelpers.h>
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#include <DataTypes/DataTypeTuple.h>
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#include <DataTypes/ObjectUtils.h>
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#include <Columns/ColumnTuple.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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    extern const int ILLEGAL_COLUMN;
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    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
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}
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namespace
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{
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class FunctionFlattenTuple : public IFunction
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{
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public:
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    static constexpr auto name = "flattenTuple";
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    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionFlattenTuple>(); }
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    String getName() const override { return name; }
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    size_t getNumberOfArguments() const override { return 1; }
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    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo &) const override { return true; }
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    bool useDefaultImplementationForConstants() const override { return true; }
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    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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    {
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        const auto & type = arguments[0];
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        const auto * type_tuple = checkAndGetDataType<DataTypeTuple>(type.get());
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        if (!type_tuple || !type_tuple->haveExplicitNames())
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            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
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                "Argument for function '{}' must be Named Tuple. Got '{}'",
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                getName(), type->getName());
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        auto [paths, types] = flattenTuple(type);
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        Names names;
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        names.reserve(paths.size());
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        for (const auto & path : paths)
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            names.push_back(path.getPath());
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        return std::make_shared<DataTypeTuple>(types, names);
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    }
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    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
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    {
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        auto column = arguments.at(0).column;
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        if (!checkAndGetColumn<ColumnTuple>(column.get()))
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            throw Exception(ErrorCodes::ILLEGAL_COLUMN,
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                "Illegal column {} of first argument of function {}. Expected ColumnTuple",
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                column->getName(), getName());
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        return flattenTuple(column);
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    }
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};
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}
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REGISTER_FUNCTION(FlattenTuple)
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{
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    factory.registerFunction<FunctionFlattenTuple>();
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}
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}
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