ClickHouse/dbms/src/Storages/MergeTree/MergeTreeReaderWide.cpp

#include <DataTypes/NestedUtils.h>
#include <DataTypes/DataTypeArray.h>
#include <Common/escapeForFileName.h>
#include <Compression/CachedCompressedReadBuffer.h>
#include <Columns/ColumnArray.h>
#include <Interpreters/evaluateMissingDefaults.h>
#include <Storages/MergeTree/MergeTreeReaderWide.h>
#include <Common/typeid_cast.h>
#include <Poco/File.h>


namespace DB
{

namespace
{
    using OffsetColumns = std::map<std::string, ColumnPtr>;

    constexpr auto DATA_FILE_EXTENSION = ".bin";
}

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
    extern const int NOT_FOUND_EXPECTED_DATA_PART;
    extern const int MEMORY_LIMIT_EXCEEDED;
    extern const int ARGUMENT_OUT_OF_BOUND;
}

MergeTreeReaderWide::MergeTreeReaderWide(const MergeTreeData::DataPartPtr & data_part_,
    const NamesAndTypesList & columns_, UncompressedCache * uncompressed_cache_, MarkCache * mark_cache_,
    const MarkRanges & mark_ranges_, const ReaderSettings & settings_, const ValueSizeMap & avg_value_size_hints_,
    const ReadBufferFromFileBase::ProfileCallback & profile_callback_,
    clockid_t clock_type_)
    : IMergeTreeReader(data_part_, columns_
    , uncompressed_cache_, mark_cache_, mark_ranges_
    , settings_, avg_value_size_hints_)
{
    try
    {
        for (const NameAndTypePair & column : columns)
            addStreams(column.name, *column.type, profile_callback_, clock_type_);
    }
    catch (...)
    {
        storage.reportBrokenPart(data_part->name);
        throw;
    }
}

size_t MergeTreeReaderWide::readRows(size_t from_mark, bool continue_reading, size_t max_rows_to_read, Block & res)
{
    std::cerr << "(MergeTreeReaderWide::readRows) columns: " << columns.toString() << "\n";
    std::cerr << "(MergeTreeReaderWide::readRows) from_rows: " << from_mark << "\n";
    std::cerr << "(MergeTreeReaderWide::readRows) block: " << res.dumpStructure() << "\n";

    size_t read_rows = 0;
    try
    {
        /// Pointers to offset columns that are common to the nested data structure columns.
        /// If append is true, then the value will be equal to nullptr and will be used only to
        /// check that the offsets column has been already read.
        OffsetColumns offset_columns;

        for (const NameAndTypePair & it : columns)
        {
            /// The column is already present in the block so we will append the values to the end.
            bool append = res.has(it.name);
            if (!append)
                res.insert(ColumnWithTypeAndName(it.type->createColumn(), it.type, it.name));

            /// To keep offsets shared. TODO Very dangerous. Get rid of this.
            MutableColumnPtr column = res.getByName(it.name).column->assumeMutable();

            bool read_offsets = true;

            /// For nested data structures collect pointers to offset columns.
            if (const DataTypeArray * type_arr = typeid_cast<const DataTypeArray *>(it.type.get()))
            {
                String name = Nested::extractTableName(it.name);

                auto it_inserted = offset_columns.emplace(name, nullptr);

                /// offsets have already been read on the previous iteration and we don't need to read it again
                if (!it_inserted.second)
                    read_offsets = false;

                /// need to create new offsets
                if (it_inserted.second && !append)
                    it_inserted.first->second = ColumnArray::ColumnOffsets::create();

                /// share offsets in all elements of nested structure
                if (!append)
                    column = ColumnArray::create(type_arr->getNestedType()->createColumn(),
                                                 it_inserted.first->second)->assumeMutable();
            }

            try
            {
                size_t column_size_before_reading = column->size();

                readData(it.name, *it.type, *column, from_mark, continue_reading, max_rows_to_read, read_offsets);

                /// For elements of Nested, column_size_before_reading may be greater than column size
                ///  if offsets are not empty and were already read, but elements are empty.
                if (column->size())
                    read_rows = std::max(read_rows, column->size() - column_size_before_reading);
            }
            catch (Exception & e)
            {
                /// Better diagnostics.
                e.addMessage("(while reading column " + it.name + ")");
                throw;
            }

            if (column->size())
                res.getByName(it.name).column = std::move(column);
            else
                res.erase(it.name);
        }

        /// NOTE: positions for all streams must be kept in sync. In particular, even if for some streams there are no rows to be read,
        /// you must ensure that no seeks are skipped and at this point they all point to to_mark.
    }
    catch (Exception & e)
    {
        if (e.code() != ErrorCodes::MEMORY_LIMIT_EXCEEDED)
            storage.reportBrokenPart(data_part->name);

        /// Better diagnostics.
        e.addMessage("(while reading from part " + path + " from mark " + toString(from_mark) + " with max_rows_to_read = " + toString(max_rows_to_read) + ")");
        throw;
    }
    catch (...)
    {
        storage.reportBrokenPart(data_part->name);

        throw;
    }

    // std::cerr << "(MergeTreeReaderWide::readRows) read_rows: " << read_rows << "\n";

    return read_rows;
}

void MergeTreeReaderWide::addStreams(const String & name, const IDataType & type,
    const ReadBufferFromFileBase::ProfileCallback & profile_callback, clockid_t clock_type)
{
    IDataType::StreamCallback callback = [&] (const IDataType::SubstreamPath & substream_path)
    {
        String stream_name = IDataType::getFileNameForStream(name, substream_path);

        if (streams.count(stream_name))
            return;

        bool data_file_exists = data_part->checksums.files.count(stream_name + DATA_FILE_EXTENSION);

        /** If data file is missing then we will not try to open it.
          * It is necessary since it allows to add new column to structure of the table without creating new files for old parts.
          */
        if (!data_file_exists)
            return;
        
        std::cerr << "(addStreams) part: " << path << '\n';
        std::cerr << "(addStreams) marks count: " << data_part->getMarksCount() << "\n";
 
        streams.emplace(stream_name, std::make_unique<MergeTreeReaderStream>(
            path + stream_name, DATA_FILE_EXTENSION, data_part->getMarksCount(),
            all_mark_ranges, settings, mark_cache,
            uncompressed_cache, data_part->getFileSizeOrZero(stream_name + DATA_FILE_EXTENSION),
            &data_part->index_granularity_info,
            profile_callback, clock_type));
    };

    IDataType::SubstreamPath substream_path;
    type.enumerateStreams(callback, substream_path);
}


void MergeTreeReaderWide::readData(
    const String & name, const IDataType & type, IColumn & column,
    size_t from_mark, bool continue_reading, size_t max_rows_to_read,
    bool with_offsets)
{
    std::cerr << "(MergeTreeReaderWide::readData) name: " << name << "\n";
    std::cerr << "(MergeTreeReaderWide::readData) max_rows_to_read: " << max_rows_to_read << "\n";
    auto get_stream_getter = [&](bool stream_for_prefix) -> IDataType::InputStreamGetter
    {
        return [&, stream_for_prefix](const IDataType::SubstreamPath & substream_path) -> ReadBuffer *
        {
            /// If offsets for arrays have already been read.
            if (!with_offsets && substream_path.size() == 1 && substream_path[0].type == IDataType::Substream::ArraySizes)
                return nullptr;

            String stream_name = IDataType::getFileNameForStream(name, substream_path);

            auto it = streams.find(stream_name);
            if (it == streams.end())
                return nullptr;

            MergeTreeReaderStream & stream = *it->second;

            if (stream_for_prefix)
            {
                stream.seekToStart();
                continue_reading = false;
            }
            else if (!continue_reading)
                stream.seekToMark(from_mark);

            return stream.data_buffer;
        };
    };

    double & avg_value_size_hint = avg_value_size_hints[name];
    IDataType::DeserializeBinaryBulkSettings settings;
    settings.avg_value_size_hint = avg_value_size_hint;

    if (deserialize_binary_bulk_state_map.count(name) == 0)
    {
        settings.getter = get_stream_getter(true);
        type.deserializeBinaryBulkStatePrefix(settings, deserialize_binary_bulk_state_map[name]);
    }

    settings.getter = get_stream_getter(false);
    settings.continuous_reading = continue_reading;
    auto & deserialize_state = deserialize_binary_bulk_state_map[name];
    type.deserializeBinaryBulkWithMultipleStreams(column, max_rows_to_read, settings, deserialize_state);
    IDataType::updateAvgValueSizeHint(column, avg_value_size_hint);
}

}