be/src/vec/functions/function_decode_varchar.cpp

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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// specific language governing permissions and limitations
// under the License.

#include <fmt/core.h>

#include <cstddef>
#include <limits>
#include <type_traits>

#include "common/exception.h"
#include "common/status.h"
#include "runtime/primitive_type.h"
#include "util/simd/reverse_copy_bytes.h"
#include "vec/columns/column_const.h"
#include "vec/columns/column_vector.h"
#include "vec/core/types.h"
#include "vec/data_types/data_type.h"
#include "vec/data_types/data_type_number.h"
#include "vec/data_types/data_type_string.h"
#include "vec/functions/function.h"
#include "vec/functions/function_helpers.h"
#include "vec/functions/simple_function_factory.h"

namespace doris::vectorized {

template <PrimitiveType IntegerPType>
class FunctionDecodeAsVarchar : public IFunction {
public:
    using IntegerType = typename PrimitiveTypeTraits<IntegerPType>::CppType;
    static constexpr auto name = "decode_as_varchar";
    static FunctionPtr create() { return std::make_shared<FunctionDecodeAsVarchar>(); }

    String get_name() const override { return name; }

    size_t get_number_of_arguments() const override { return 1; }

    bool is_variadic() const override { return true; }

    DataTypes get_variadic_argument_types_impl() const override {
        return {std::make_shared<typename PrimitiveTypeTraits<IntegerPType>::DataType>()};
    }

    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {
        if (arguments.size() != 1) {
            throw doris::Exception(ErrorCode::INVALID_ARGUMENT,
                                   "Function {} requires 1 arguments, got {}", name,
                                   arguments.size());
        }

        return std::make_shared<DataTypeString>();
    }

    Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,
                        uint32_t result, size_t input_rows_count) const override {
        const auto* col_source =
                assert_cast<const typename PrimitiveTypeTraits<IntegerPType>::ColumnType*>(
                        block.get_by_position(arguments[0]).column.get());

        auto col_res = ColumnString::create();

        ColumnString::Chars& col_res_data = col_res->get_chars();
        ColumnString::Offsets& col_res_offset = col_res->get_offsets();
        col_res_data.resize(input_rows_count * sizeof(IntegerType));
        col_res_offset.resize(input_rows_count);

        for (Int32 i = 0; i < input_rows_count; ++i) {
            IntegerType value = col_source->get_element(i);
            const auto* const __restrict ui8_ptr = reinterpret_cast<const UInt8*>(&value);
            UInt32 str_size = static_cast<UInt32>(*ui8_ptr) & 0x7F;

            if (str_size >= sizeof(IntegerType)) {
                const auto& type_ptr = block.get_by_position(arguments[0]).type;
                throw doris::Exception(ErrorCode::INVALID_ARGUMENT,
                                       "Invalid input of function {}, input type {} value {}, "
                                       "string size {}, should not be larger than {}",
                                       name, type_ptr->get_name(), value, str_size,
                                       sizeof(IntegerType));
            }

            // col_res_offset[-1] is valid for PaddedPODArray, will get 0
            col_res_offset[i] = col_res_offset[i - 1] + str_size;
            value <<= 1;

            simd::reverse_copy_bytes(col_res_data.data() + col_res_offset[i - 1], str_size,
                                     ui8_ptr + sizeof(IntegerType) - str_size, str_size);
        }
        col_res_data.resize(col_res_offset[col_res_offset.size() - 1]);

        block.get_by_position(result).column = std::move(col_res);

        return Status::OK();
    }
};

void register_function_decode_as_varchar(SimpleFunctionFactory& factory) {
    factory.register_function<FunctionDecodeAsVarchar<TYPE_SMALLINT>>();
    factory.register_function<FunctionDecodeAsVarchar<TYPE_INT>>();
    factory.register_function<FunctionDecodeAsVarchar<TYPE_BIGINT>>();
    factory.register_function<FunctionDecodeAsVarchar<TYPE_LARGEINT>>();
}

} // namespace doris::vectorized