ClickHouse/src/DataTypes/DataTypeOneElementTuple.cpp

#include <DataTypes/DataTypeOneElementTuple.h>
#include <DataTypes/DataTypeFactory.h>
#include <DataTypes/DataTypeCustom.h>
#include <IO/WriteBufferFromString.h>
#include <IO/Operators.h>
#include <Common/quoteString.h>
#include <Parsers/ASTNameTypePair.h>
#include <Columns/IColumn.h>


namespace DB
{

namespace
{

/** Custom substreams representation for single subcolumn.
  * It serializes/deserializes column as a nested type, but in that way
  * if it was a named tuple with one element and a given name.
  */
class DataTypeOneElementTupleStreams : public IDataTypeCustomStreams
{
private:
    DataTypePtr nested;
    String name;
    bool escape_delimiter;

public:
    DataTypeOneElementTupleStreams(const DataTypePtr & nested_, const String & name_, bool escape_delimiter_)
        : nested(nested_), name(name_), escape_delimiter(escape_delimiter_) {}

    void enumerateStreams(
        const IDataType::StreamCallback & callback,
        IDataType::SubstreamPath & path) const override
    {
        addToPath(path);
        nested->enumerateStreams(callback, path);
        path.pop_back();
    }

    void serializeBinaryBulkStatePrefix(
        IDataType:: SerializeBinaryBulkSettings & settings,
        IDataType::SerializeBinaryBulkStatePtr & state) const override
    {
        addToPath(settings.path);
        nested->serializeBinaryBulkStatePrefix(settings, state);
        settings.path.pop_back();
    }

    void serializeBinaryBulkStateSuffix(
        IDataType::SerializeBinaryBulkSettings & settings,
        IDataType::SerializeBinaryBulkStatePtr & state) const override
    {
        addToPath(settings.path);
        nested->serializeBinaryBulkStateSuffix(settings, state);
        settings.path.pop_back();
    }

    void deserializeBinaryBulkStatePrefix(
        IDataType::DeserializeBinaryBulkSettings & settings,
        IDataType::DeserializeBinaryBulkStatePtr & state) const override
    {
        addToPath(settings.path);
        nested->deserializeBinaryBulkStatePrefix(settings, state);
        settings.path.pop_back();
    }

    void serializeBinaryBulkWithMultipleStreams(
        const IColumn & column,
        size_t offset,
        size_t limit,
        IDataType::SerializeBinaryBulkSettings & settings,
        IDataType::SerializeBinaryBulkStatePtr & state) const override
    {
        addToPath(settings.path);
        nested->serializeBinaryBulkWithMultipleStreams(column, offset, limit, settings, state);
        settings.path.pop_back();
    }

    void deserializeBinaryBulkWithMultipleStreams(
        ColumnPtr & column,
        size_t limit,
        IDataType::DeserializeBinaryBulkSettings & settings,
        IDataType::DeserializeBinaryBulkStatePtr & state,
        IDataType::SubstreamsCache * cache) const override
    {
        addToPath(settings.path);
        nested->deserializeBinaryBulkWithMultipleStreams(column, limit, settings, state, cache);
        settings.path.pop_back();
    }

private:
    void addToPath(IDataType::SubstreamPath & path) const
    {
        path.push_back(IDataType::Substream::TupleElement);
        path.back().tuple_element_name = name;
        path.back().escape_tuple_delimiter = escape_delimiter;
    }
};

}

DataTypePtr createOneElementTuple(const DataTypePtr & type, const String & name, bool escape_delimiter)
{
    auto custom_desc = std::make_unique<DataTypeCustomDesc>(
        std::make_unique<DataTypeCustomFixedName>(type->getName()),nullptr,
        std::make_unique<DataTypeOneElementTupleStreams>(type, name, escape_delimiter));

    return DataTypeFactory::instance().getCustom(std::move(custom_desc));
}

}