ClickHouse/dbms/src/Storages/StorageMergeTree.cpp

#include <experimental/optional>
#include <Core/FieldVisitors.h>
#include <Storages/StorageMergeTree.h>
#include <Storages/MergeTree/MergeTreeBlockOutputStream.h>
#include <Storages/MergeTree/DiskSpaceMonitor.h>
#include <Storages/MergeTree/MergeList.h>
#include <Databases/IDatabase.h>
#include <Common/escapeForFileName.h>
#include <Interpreters/InterpreterAlterQuery.h>
#include <Interpreters/PartLog.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTSelectQuery.h>
#include <Storages/MergeTree/MergeTreeData.h>

#include <Poco/DirectoryIterator.h>
#include <Poco/File.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int ABORTED;
    extern const int BAD_ARGUMENTS;
}


StorageMergeTree::StorageMergeTree(
    const String & path_,
    const String & database_name_,
    const String & table_name_,
    NamesAndTypesListPtr columns_,
    const NamesAndTypesList & materialized_columns_,
    const NamesAndTypesList & alias_columns_,
    const ColumnDefaults & column_defaults_,
    bool attach,
    Context & context_,
    ASTPtr & primary_expr_ast_,
    const String & date_column_name_,
    const ASTPtr & sampling_expression_, /// nullptr, if sampling is not supported.
    size_t index_granularity_,
    const MergeTreeData::MergingParams & merging_params_,
    bool has_force_restore_data_flag,
    const MergeTreeSettings & settings_)
    : IStorage{materialized_columns_, alias_columns_, column_defaults_},
    path(path_), database_name(database_name_), table_name(table_name_), full_path(path + escapeForFileName(table_name) + '/'),
    context(context_), background_pool(context_.getBackgroundPool()),
    data(database_name, table_name,
         full_path, columns_,
         materialized_columns_, alias_columns_, column_defaults_,
         context_, primary_expr_ast_, date_column_name_,
         sampling_expression_, index_granularity_, merging_params_,
         settings_, database_name_ + "." + table_name, false, attach),
    reader(data), writer(data, context), merger(data, context.getBackgroundPool()),
    log(&Logger::get(database_name_ + "." + table_name + " (StorageMergeTree)"))
{
    data.loadDataParts(has_force_restore_data_flag);
    data.clearOldParts();

    /// Temporary directories contain incomplete results of merges (after forced restart)
    ///  and don't allow to reinitialize them, so delete each of them immediately
    data.clearOldTemporaryDirectories(0);

    increment.set(data.getMaxDataPartIndex());
}


void StorageMergeTree::startup()
{
    merge_task_handle = background_pool.addTask([this] { return mergeTask(); });
}


void StorageMergeTree::shutdown()
{
    if (shutdown_called)
        return;
    shutdown_called = true;
    merger.cancelForever();
    background_pool.removeTask(merge_task_handle);
}


StorageMergeTree::~StorageMergeTree()
{
    shutdown();
}

BlockInputStreams StorageMergeTree::read(
    const Names & column_names,
    const ASTPtr & query,
    const Context & context,
    QueryProcessingStage::Enum & processed_stage,
    const size_t max_block_size,
    const unsigned num_streams)
{
    return reader.read(column_names, query, context, processed_stage, max_block_size, num_streams, nullptr, 0);
}

BlockOutputStreamPtr StorageMergeTree::write(const ASTPtr & query, const Settings & settings)
{
    return std::make_shared<MergeTreeBlockOutputStream>(*this);
}

bool StorageMergeTree::checkTableCanBeDropped() const
{
    const_cast<MergeTreeData &>(getData()).recalculateColumnSizes();
    context.checkTableCanBeDropped(database_name, table_name, getData().getTotalCompressedSize());
    return true;
}

void StorageMergeTree::drop()
{
    shutdown();
    data.dropAllData();
}

void StorageMergeTree::rename(const String & new_path_to_db, const String & new_database_name, const String & new_table_name)
{
    std::string new_full_path = new_path_to_db + escapeForFileName(new_table_name) + '/';

    data.setPath(new_full_path, true);

    path = new_path_to_db;
    table_name = new_table_name;
    full_path = new_full_path;

    /// NOTE: Logger names are not updated.
}

void StorageMergeTree::alter(
    const AlterCommands & params,
    const String & database_name,
    const String & table_name,
    const Context & context)
{
    /// NOTE: Here, as in ReplicatedMergeTree, you can do ALTER which does not block the writing of data for a long time.
    auto merge_blocker = merger.cancel();

    auto table_soft_lock = lockDataForAlter();

    data.checkAlter(params);

    auto new_columns = data.getColumnsListNonMaterialized();
    auto new_materialized_columns = data.materialized_columns;
    auto new_alias_columns = data.alias_columns;
    auto new_column_defaults = data.column_defaults;

    params.apply(new_columns, new_materialized_columns, new_alias_columns, new_column_defaults);

    auto columns_for_parts = new_columns;
    columns_for_parts.insert(std::end(columns_for_parts),
        std::begin(new_materialized_columns), std::end(new_materialized_columns));

    std::vector<MergeTreeData::AlterDataPartTransactionPtr> transactions;

    bool primary_key_is_modified = false;
    ASTPtr new_primary_key_ast = data.primary_expr_ast;

    for (const AlterCommand & param : params)
    {
        if (param.type == AlterCommand::MODIFY_PRIMARY_KEY)
        {
            primary_key_is_modified = true;
            new_primary_key_ast = param.primary_key;
        }
    }

    if (primary_key_is_modified && data.merging_params.mode == MergeTreeData::MergingParams::Unsorted)
        throw Exception("UnsortedMergeTree cannot have primary key", ErrorCodes::BAD_ARGUMENTS);

    if (primary_key_is_modified && supportsSampling())
        throw Exception("MODIFY PRIMARY KEY only supported for tables without sampling key", ErrorCodes::BAD_ARGUMENTS);

    MergeTreeData::DataParts parts = data.getAllDataParts();
    for (const MergeTreeData::DataPartPtr & part : parts)
        if (auto transaction = data.alterDataPart(part, columns_for_parts, new_primary_key_ast, false))
            transactions.push_back(std::move(transaction));

    auto table_hard_lock = lockStructureForAlter();

    IDatabase::ASTModifier engine_modifier;
    if (primary_key_is_modified)
        engine_modifier = [&new_primary_key_ast] (ASTPtr & engine_ast)
        {
            auto tuple = std::make_shared<ASTFunction>(new_primary_key_ast->range);
            tuple->name = "tuple";
            tuple->arguments = new_primary_key_ast;
            tuple->children.push_back(tuple->arguments);

            /// Primary key is in the second place in table engine description and can be represented as a tuple.
            /// TODO: Not always in second place. If there is a sampling key, then the third one. Fix it.
            typeid_cast<ASTExpressionList &>(*typeid_cast<ASTFunction &>(*engine_ast).arguments).children.at(1) = tuple;
        };

    context.getDatabase(database_name)->alterTable(
        context, table_name,
        new_columns, new_materialized_columns, new_alias_columns, new_column_defaults,
        engine_modifier);

    materialized_columns = new_materialized_columns;
    alias_columns = new_alias_columns;
    column_defaults = new_column_defaults;

    data.setColumnsList(new_columns);
    data.materialized_columns = std::move(new_materialized_columns);
    data.alias_columns = std::move(new_alias_columns);
    data.column_defaults = std::move(new_column_defaults);

    if (primary_key_is_modified)
    {
        data.primary_expr_ast = new_primary_key_ast;
    }
    /// Reinitialize primary key because primary key column types might have changed.
    data.initPrimaryKey();

    for (auto & transaction : transactions)
        transaction->commit();

    /// Columns sizes could be changed
    data.recalculateColumnSizes();

    if (primary_key_is_modified)
        data.loadDataParts(false);
}


/// While exists, marks parts as 'currently_merging' and reserves free space on filesystem.
/// It's possible to mark parts before.
struct CurrentlyMergingPartsTagger
{
    MergeTreeData::DataPartsVector parts;
    DiskSpaceMonitor::ReservationPtr reserved_space;
    StorageMergeTree * storage = nullptr;

    CurrentlyMergingPartsTagger() = default;

    CurrentlyMergingPartsTagger(const MergeTreeData::DataPartsVector & parts_, size_t total_size, StorageMergeTree & storage_)
        : parts(parts_), storage(&storage_)
    {
        /// Assume mutex is already locked, because this method is called from mergeTask.
        reserved_space = DiskSpaceMonitor::reserve(storage->full_path, total_size); /// May throw.
        for (const auto & part : parts)
        {
            if (storage->currently_merging.count(part))
                throw Exception("Tagging alreagy tagged part " + part->name + ". This is a bug.", ErrorCodes::LOGICAL_ERROR);
        }
        storage->currently_merging.insert(parts.begin(), parts.end());
    }

    ~CurrentlyMergingPartsTagger()
    {
        std::lock_guard<std::mutex> lock(storage->currently_merging_mutex);

        for (const auto & part : parts)
        {
            if (!storage->currently_merging.count(part))
                std::terminate();
            storage->currently_merging.erase(part);
        }
    }
};


bool StorageMergeTree::merge(
    size_t aio_threshold,
    bool aggressive,
    const String & partition,
    bool final,
    bool deduplicate)
{
    /// Clear old parts. It does not matter to do it more frequently than each second.
    if (auto lock = time_after_previous_cleanup.lockTestAndRestartAfter(1))
    {
        data.clearOldParts();
        data.clearOldTemporaryDirectories();
    }

    auto structure_lock = lockStructure(true);

    size_t disk_space = DiskSpaceMonitor::getUnreservedFreeSpace(full_path);

    /// You must call destructor under unlocked `currently_merging_mutex`.
    std::experimental::optional<CurrentlyMergingPartsTagger> merging_tagger;
    String merged_name;

    {
        std::lock_guard<std::mutex> lock(currently_merging_mutex);

        MergeTreeData::DataPartsVector parts;

        auto can_merge = [this] (const MergeTreeData::DataPartPtr & left, const MergeTreeData::DataPartPtr & right)
        {
            return !currently_merging.count(left) && !currently_merging.count(right);
        };

        bool selected = false;

        if (partition.empty())
        {
            size_t max_parts_size_for_merge = merger.getMaxPartsSizeForMerge();
            if (max_parts_size_for_merge > 0)
                selected = merger.selectPartsToMerge(parts, merged_name, aggressive, max_parts_size_for_merge, can_merge);
        }
        else
        {
            DayNum_t month = MergeTreeData::getMonthFromName(partition);
            selected = merger.selectAllPartsToMergeWithinPartition(parts, merged_name, disk_space, can_merge, month, final);
        }

        if (!selected)
            return false;

        merging_tagger.emplace(parts, MergeTreeDataMerger::estimateDiskSpaceForMerge(parts), *this);
    }

    MergeList::EntryPtr merge_entry_ptr = context.getMergeList().insert(database_name, table_name, merged_name, merging_tagger->parts);

    /// Logging
    Stopwatch stopwatch;

    auto new_part = merger.mergePartsToTemporaryPart(
        merging_tagger->parts, merged_name, *merge_entry_ptr, aio_threshold, time(0), merging_tagger->reserved_space.get(), deduplicate);

    merger.renameMergedTemporaryPart(merging_tagger->parts, new_part, merged_name, nullptr);

    if (auto part_log = context.getPartLog(database_name, table_name))
    {
        PartLogElement elem;
        elem.event_time = time(0);

        elem.merged_from.reserve(merging_tagger->parts.size());
        for (const auto & part : merging_tagger->parts)
            elem.merged_from.push_back(part->name);
        elem.event_type = PartLogElement::MERGE_PARTS;
        elem.size_in_bytes = new_part->size_in_bytes;

        elem.database_name = new_part->storage.getDatabaseName();
        elem.table_name = new_part->storage.getTableName();
        elem.part_name = new_part->name;

        elem.duration_ms = stopwatch.elapsed() / 1000000;

        part_log->add(elem);

        elem.duration_ms = 0;
        elem.event_type = PartLogElement::REMOVE_PART;
        elem.merged_from = Strings();

        for (const auto & part : merging_tagger->parts)
        {
            elem.part_name = part->name;
            elem.size_in_bytes = part->size_in_bytes;
            part_log->add(elem);
        }
    }

    return true;
}

bool StorageMergeTree::mergeTask()
{
    if (shutdown_called)
        return false;

    try
    {
        size_t aio_threshold = context.getSettings().min_bytes_to_use_direct_io;
        return merge(aio_threshold, false /*aggressive*/, {} /*partition*/, false /*final*/, false /*deduplicate*/); ///TODO: read deduplicate option from table config
    }
    catch (Exception & e)
    {
        if (e.code() == ErrorCodes::ABORTED)
        {
            LOG_INFO(log, e.message());
            return false;
        }

        throw;
    }
}

void StorageMergeTree::dropColumnFromPartition(const ASTPtr & query, const Field & partition, const Field & column_name, const Settings &)
{
    /// Asks to complete merges and does not allow them to start.
    /// This protects against "revival" of data for a removed partition after completion of merge.
    auto merge_blocker = merger.cancel();
    /// Waits for completion of merge and does not start new ones.
    auto lock = lockForAlter();

    DayNum_t month = MergeTreeData::getMonthDayNum(partition);
    MergeTreeData::DataParts parts = data.getDataParts();

    std::vector<MergeTreeData::AlterDataPartTransactionPtr> transactions;

    AlterCommand alter_command;
    alter_command.type = AlterCommand::DROP_COLUMN;
    alter_command.column_name = get<String>(column_name);

    auto new_columns = data.getColumnsListNonMaterialized();
    auto new_materialized_columns = data.materialized_columns;
    auto new_alias_columns = data.alias_columns;
    auto new_column_defaults = data.column_defaults;

    alter_command.apply(new_columns, new_materialized_columns, new_alias_columns, new_column_defaults);

    auto columns_for_parts = new_columns;
    columns_for_parts.insert(std::end(columns_for_parts),
        std::begin(new_materialized_columns), std::end(new_materialized_columns));

    for (const auto & part : parts)
    {
        if (part->month != month)
            continue;

        if (auto transaction = data.alterDataPart(part, columns_for_parts, data.primary_expr_ast, false))
            transactions.push_back(std::move(transaction));

        LOG_DEBUG(log, "Removing column " << get<String>(column_name) << " from part " << part->name);
    }

    if (transactions.empty())
        return;

    for (auto & transaction : transactions)
        transaction->commit();
}

void StorageMergeTree::dropPartition(const ASTPtr & query, const Field & partition, bool detach, const Settings & settings)
{
    /// Asks to complete merges and does not allow them to start.
    /// This protects against "revival" of data for a removed partition after completion of merge.
    auto merge_blocker = merger.cancel();
    /// Waits for completion of merge and does not start new ones.
    auto lock = lockForAlter();

    DayNum_t month = MergeTreeData::getMonthDayNum(partition);

    size_t removed_parts = 0;
    MergeTreeData::DataParts parts = data.getDataParts();

    for (const auto & part : parts)
    {
        if (part->month != month)
            continue;

        LOG_DEBUG(log, "Removing part " << part->name);
        ++removed_parts;

        if (detach)
            data.renameAndDetachPart(part, "");
        else
            data.replaceParts({part}, {}, false);
    }

    LOG_INFO(log, (detach ? "Detached " : "Removed ") << removed_parts << " parts inside " << applyVisitor(FieldVisitorToString(), partition) << ".");
}


void StorageMergeTree::attachPartition(const ASTPtr & query, const Field & field, bool part, const Settings & settings)
{
    String partition;

    if (part)
        partition = field.getType() == Field::Types::UInt64 ? toString(field.get<UInt64>()) : field.safeGet<String>();
    else
        partition = MergeTreeData::getMonthName(field);

    String source_dir = "detached/";

    /// Let's make a list of parts to add.
    Strings parts;
    if (part)
    {
        parts.push_back(partition);
    }
    else
    {
        LOG_DEBUG(log, "Looking for parts for partition " << partition << " in " << source_dir);
        ActiveDataPartSet active_parts;
        for (Poco::DirectoryIterator it = Poco::DirectoryIterator(full_path + source_dir); it != Poco::DirectoryIterator(); ++it)
        {
            String name = it.name();
            if (!ActiveDataPartSet::isPartDirectory(name))
                continue;
            if (name.substr(0, partition.size()) != partition)
                continue;
            LOG_DEBUG(log, "Found part " << name);
            active_parts.add(name);
        }
        LOG_DEBUG(log, active_parts.size() << " of them are active");
        parts = active_parts.getParts();
    }

    for (const auto & source_part_name : parts)
    {
        String source_path = source_dir + source_part_name;

        LOG_DEBUG(log, "Checking data");
        MergeTreeData::MutableDataPartPtr part = data.loadPartAndFixMetadata(source_path);

        LOG_INFO(log, "Attaching part " << source_part_name << " from " << source_path);
        data.renameTempPartAndAdd(part, &increment);

        LOG_INFO(log, "Finished attaching part");
    }

    /// New parts with other data may appear in place of deleted parts.
    context.resetCaches();
}


void StorageMergeTree::freezePartition(const Field & partition, const String & with_name, const Settings & settings)
{
    /// The prefix can be arbitrary. Not necessarily a month - you can specify only a year.
    data.freezePartition(partition.getType() == Field::Types::UInt64
        ? toString(partition.get<UInt64>())
        : partition.safeGet<String>(), with_name);
}

}