ClickHouse

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#include <Functions/IFunction.h>
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#include <Functions/castTypeToEither.h>
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#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypesNumber.h>
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#include <DataTypes/DataTypeNullable.h>
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#include <Core/ColumnNumbers.h>
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#include <Columns/ColumnNullable.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 BAD_ARGUMENTS;
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    extern const int ILLEGAL_COLUMN;
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}
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namespace
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{
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/// Returns 1 if argument is zero or NULL.
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/// It can be used to negate filter in WHERE condition.
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/// "WHERE isZeroOrNull(expr)" will return exactly the same rows that "WHERE expr" will filter out.
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class FunctionIsZeroOrNull : public IFunction
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{
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public:
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    static constexpr auto name = "isZeroOrNull";
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    static FunctionPtr create(ContextPtr)
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    {
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        return std::make_shared<FunctionIsZeroOrNull>();
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    }
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    std::string getName() const override
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    {
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        return name;
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    }
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    size_t getNumberOfArguments() const override { return 1; }
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    bool useDefaultImplementationForNulls() const override { return false; }
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    bool useDefaultImplementationForConstants() const override { return true; }
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    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
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    ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
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    DataTypePtr getReturnTypeImpl(const DataTypes & types) const override
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    {
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        if (!isNumber(removeNullable(types.at(0))) && !isNothing(removeNullable(types.at(0))))
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            throw Exception(
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                ErrorCodes::BAD_ARGUMENTS, "The argument of function {} must have simple numeric type, possibly Nullable or Null", name);
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        return std::make_shared<DataTypeUInt8>();
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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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        if (isNothing(removeNullable(arguments[0].type)))
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            return DataTypeUInt8{}.createColumnConst(input_rows_count, 1);
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        const ColumnPtr & input_column = arguments[0].column;
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        ColumnPtr res;
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        if (const ColumnNullable * input_column_nullable = checkAndGetColumn<ColumnNullable>(input_column.get()))
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        {
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            const NullMap & null_map = input_column_nullable->getNullMapData();
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            const IColumn * nested_column = &input_column_nullable->getNestedColumn();
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            if (!castTypeToEither<
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                ColumnUInt8, ColumnUInt16, ColumnUInt32, ColumnUInt64,
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                ColumnInt8, ColumnInt16, ColumnInt32, ColumnInt64,
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                ColumnFloat32, ColumnFloat64>(
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                nested_column, [&](const auto & column)
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                {
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                    auto col = ColumnUInt8::create(input_rows_count);
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                    processNullable(column.getData(), null_map, col->getData(), input_rows_count);
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                    res = std::move(col);
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                    return true;
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                }))
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            {
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                throw Exception(
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                    ErrorCodes::ILLEGAL_COLUMN,
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                    "The argument of function {} must have simple numeric type, possibly Nullable or Null",
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                    name);
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            }
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        }
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        else
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        {
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            if (!castTypeToEither<
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                ColumnUInt8, ColumnUInt16, ColumnUInt32, ColumnUInt64,
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                ColumnInt8, ColumnInt16, ColumnInt32, ColumnInt64,
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                ColumnFloat32, ColumnFloat64>(
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                input_column.get(), [&](const auto & column)
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                {
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                    auto col = ColumnUInt8::create(input_rows_count);
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                    processNotNullable(column.getData(), col->getData(), input_rows_count);
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                    res = std::move(col);
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                    return true;
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                }))
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            {
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                throw Exception(
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                    ErrorCodes::ILLEGAL_COLUMN,
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                    "The argument of function {} must have simple numeric type, possibly Nullable or Null",
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                    name);
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            }
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        }
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        return res;
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    }
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private:
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    template <typename InputData>
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    void processNotNullable(const InputData & input_data, ColumnUInt8::Container & result_data, size_t input_rows_count) const
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    {
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        for (size_t i = 0; i < input_rows_count; ++i)
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            result_data[i] = input_data[i] == 0;
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    }
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    template <typename InputData>
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    void processNullable(const InputData & input_data, const NullMap & input_null_map,
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        ColumnUInt8::Container & result_data, size_t input_rows_count) const
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    {
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        for (size_t i = 0; i < input_rows_count; ++i)
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            result_data[i] = input_null_map[i] || input_data[i] == 0;
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    }
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};
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}
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REGISTER_FUNCTION(IsZeroOrNull)
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{
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    factory.registerFunction<FunctionIsZeroOrNull>();
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}
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}
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