ClickHouse/src/Interpreters/ConcurrentHashJoin.cpp

#include <memory>
#include <mutex>
#include <Columns/ColumnSparse.h>
#include <Columns/FilterDescription.h>
#include <Columns/IColumn.h>
#include <Core/ColumnsWithTypeAndName.h>
#include <Core/NamesAndTypes.h>
#include <Interpreters/ConcurrentHashJoin.h>
#include <Interpreters/Context.h>
#include <Interpreters/ExpressionActions.h>
#include <Interpreters/PreparedSets.h>
#include <Interpreters/TableJoin.h>
#include <Interpreters/createBlockSelector.h>
#include <Parsers/DumpASTNode.h>
#include <Parsers/ExpressionListParsers.h>
#include <Parsers/IAST_fwd.h>
#include <Parsers/parseQuery.h>
#include <Common/Exception.h>
#include <Common/WeakHash.h>
#include <Common/typeid_cast.h>
#include <DataTypes/DataTypeLowCardinality.h>

namespace DB
{

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
    extern const int SET_SIZE_LIMIT_EXCEEDED;
}

static UInt32 toPowerOfTwo(UInt32 x)
{
    if (x <= 1)
        return 1;
    return static_cast<UInt32>(1) << (32 - std::countl_zero(x - 1));
}

ConcurrentHashJoin::ConcurrentHashJoin(ContextPtr context_, std::shared_ptr<TableJoin> table_join_, size_t slots_, const Block & right_sample_block, bool any_take_last_row_)
    : context(context_)
    , table_join(table_join_)
    , slots(toPowerOfTwo(std::min<UInt32>(static_cast<UInt32>(slots_), 256)))
{
    for (size_t i = 0; i < slots; ++i)
    {
        auto inner_hash_join = std::make_shared<InternalHashJoin>();

        inner_hash_join->data = std::make_unique<HashJoin>(table_join_, right_sample_block, any_take_last_row_, 0, fmt::format("concurrent{}", i));
        /// Non zero `max_joined_block_rows` allows to process block partially and return not processed part.
        /// TODO: It's not handled properly in ConcurrentHashJoin case, so we set it to 0 to disable this feature.
        inner_hash_join->data->setMaxJoinedBlockRows(0);
        hash_joins.emplace_back(std::move(inner_hash_join));
    }
}

bool ConcurrentHashJoin::addBlockToJoin(const Block & right_block, bool check_limits)
{
    Blocks dispatched_blocks = dispatchBlock(table_join->getOnlyClause().key_names_right, right_block);

    size_t blocks_left = 0;
    for (const auto & block : dispatched_blocks)
    {
        if (block)
        {
            ++blocks_left;
        }
    }

    while (blocks_left > 0)
    {
        /// insert blocks into corresponding HashJoin instances
        for (size_t i = 0; i < dispatched_blocks.size(); ++i)
        {
            auto & hash_join = hash_joins[i];
            auto & dispatched_block = dispatched_blocks[i];

            if (dispatched_block)
            {
                /// if current hash_join is already processed by another thread, skip it and try later
                std::unique_lock<std::mutex> lock(hash_join->mutex, std::try_to_lock);
                if (!lock.owns_lock())
                    continue;

                bool limit_exceeded = !hash_join->data->addBlockToJoin(dispatched_block, check_limits);

                dispatched_block = {};
                blocks_left--;

                if (limit_exceeded)
                    return false;
            }
        }
    }

    if (check_limits)
        return table_join->sizeLimits().check(getTotalRowCount(), getTotalByteCount(), "JOIN", ErrorCodes::SET_SIZE_LIMIT_EXCEEDED);
    return true;
}

void ConcurrentHashJoin::joinBlock(Block & block, std::shared_ptr<ExtraBlock> & /*not_processed*/)
{
    Blocks dispatched_blocks = dispatchBlock(table_join->getOnlyClause().key_names_left, block);
    block = {};
    for (size_t i = 0; i < dispatched_blocks.size(); ++i)
    {
        std::shared_ptr<ExtraBlock> none_extra_block;
        auto & hash_join = hash_joins[i];
        auto & dispatched_block = dispatched_blocks[i];
        hash_join->data->joinBlock(dispatched_block, none_extra_block);
        if (none_extra_block && !none_extra_block->empty())
            throw Exception(ErrorCodes::LOGICAL_ERROR, "not_processed should be empty");
    }

    block = concatenateBlocks(dispatched_blocks);
}

void ConcurrentHashJoin::checkTypesOfKeys(const Block & block) const
{
    hash_joins[0]->data->checkTypesOfKeys(block);
}

void ConcurrentHashJoin::setTotals(const Block & block)
{
    if (block)
    {
        std::lock_guard lock(totals_mutex);
        totals = block;
    }
}

const Block & ConcurrentHashJoin::getTotals() const
{
    return totals;
}

size_t ConcurrentHashJoin::getTotalRowCount() const
{
    size_t res = 0;
    for (const auto & hash_join : hash_joins)
    {
        std::lock_guard lock(hash_join->mutex);
        res += hash_join->data->getTotalRowCount();
    }
    return res;
}

size_t ConcurrentHashJoin::getTotalByteCount() const
{
    size_t res = 0;
    for (const auto & hash_join : hash_joins)
    {
        std::lock_guard lock(hash_join->mutex);
        res += hash_join->data->getTotalByteCount();
    }
    return res;
}

bool ConcurrentHashJoin::alwaysReturnsEmptySet() const
{
    for (const auto & hash_join : hash_joins)
    {
        std::lock_guard lock(hash_join->mutex);
        if (!hash_join->data->alwaysReturnsEmptySet())
            return false;
    }
    return true;
}

IBlocksStreamPtr ConcurrentHashJoin::getNonJoinedBlocks(
        const Block & /*left_sample_block*/, const Block & /*result_sample_block*/, UInt64 /*max_block_size*/) const
{
    if (!JoinCommon::hasNonJoinedBlocks(*table_join))
        return {};

    throw Exception(ErrorCodes::LOGICAL_ERROR, "Invalid join type. join kind: {}, strictness: {}",
                    table_join->kind(), table_join->strictness());
}

static ALWAYS_INLINE IColumn::Selector hashToSelector(const WeakHash32 & hash, size_t num_shards)
{
    assert(num_shards > 0 && (num_shards & (num_shards - 1)) == 0);
    const auto & data = hash.getData();
    size_t num_rows = data.size();

    IColumn::Selector selector(num_rows);
    for (size_t i = 0; i < num_rows; ++i)
        /// Apply intHash64 to mix bits in data.
        /// HashTable internally uses WeakHash32, and we need to get different lower bits not to cause collisions.
        selector[i] = intHash64(data[i]) & (num_shards - 1);
    return selector;
}

IColumn::Selector ConcurrentHashJoin::selectDispatchBlock(const Strings & key_columns_names, const Block & from_block)
{
    size_t num_rows = from_block.rows();
    size_t num_shards = hash_joins.size();

    WeakHash32 hash(num_rows);
    for (const auto & key_name : key_columns_names)
    {
        const auto & key_col = from_block.getByName(key_name).column->convertToFullColumnIfConst();
        const auto & key_col_no_lc = recursiveRemoveLowCardinality(recursiveRemoveSparse(key_col));
        key_col_no_lc->updateWeakHash32(hash);
    }
    return hashToSelector(hash, num_shards);
}

Blocks ConcurrentHashJoin::dispatchBlock(const Strings & key_columns_names, const Block & from_block)
{
    /// TODO: use JoinCommon::scatterBlockByHash
    size_t num_shards = hash_joins.size();
    size_t num_cols = from_block.columns();

    IColumn::Selector selector = selectDispatchBlock(key_columns_names, from_block);

    Blocks result(num_shards);
    for (size_t i = 0; i < num_shards; ++i)
        result[i] = from_block.cloneEmpty();

    for (size_t i = 0; i < num_cols; ++i)
    {
        auto dispatched_columns = from_block.getByPosition(i).column->scatter(num_shards, selector);
        assert(result.size() == dispatched_columns.size());
        for (size_t block_index = 0; block_index < num_shards; ++block_index)
        {
            result[block_index].getByPosition(i).column = std::move(dispatched_columns[block_index]);
        }
    }
    return result;
}

}