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ClickHouse/src/Storages/StorageBuffer.cpp
Azat Khuzhin b0a80af888 Reduce lock contention for multiple layers of the Buffer engine 
Otherwise you can see something like this for the following query:

    ```sql
    WITH
        arrayMap(x -> demangle(addressToSymbol(x)), s.trace) AS trace_array,
        arrayStringConcat(trace_array, '\n') AS trace_string
    SELECT
        p.thread_id,
        p.query_id,
        p.query,
        trace_string
    FROM
    (
        SELECT
            query_id,
            query,
            arrayJoin(thread_ids) AS thread_id
        FROM system.processes
    ) AS p
    INNER JOIN system.stack_trace AS s ON p.thread_id = s.thread_id
    ORDER BY p.query_id ASC
    SETTINGS enable_global_with_statement = 0, allow_introspection_functions = 1
    FORMAT PrettyCompactNoEscapes
    ```

Lots of the following:

    ```sql
    INSERT INTO buffer (...) VALUES

    __lll_lock_wait
    pthread_mutex_lock
    std::__1::mutex::lock()
    DB::StorageBuffer::reschedule()
    DB::BufferBlockOutputStream::write(DB::Block const&)
    ```

That will wait one of this:

    ```
    INSERT INTO buffer (...) VALUES

    ...
    DB::PushingToViewsBlockOutputStream::write(DB::Block const&)
    DB::AddingDefaultBlockOutputStream::write(DB::Block const&)
    DB::SquashingBlockOutputStream::finalize()
    DB::SquashingBlockOutputStream::writeSuffix()
    DB::PushingToViewsBlockOutputStream::writeSuffix()
    DB::StorageBuffer::writeBlockToDestination(DB::Block const&, std::__1::shared_ptr<DB::IStorage>)
    DB::StorageBuffer::flushBuffer(DB::StorageBuffer::Buffer&, bool, bool, bool)
    ```

P.S. we cannot simply unlock the buffer during flushing, see comments in
the code
2021-01-21 22:09:24 +03:00

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#include <boost/range/algorithm_ext/erase.hpp>
#include <Interpreters/InterpreterSelectQuery.h>
#include <Interpreters/InterpreterInsertQuery.h>
#include <Interpreters/InterpreterAlterQuery.h>
#include <Interpreters/castColumn.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <Processors/QueryPlan/AddingMissedStep.h>
#include <DataStreams/IBlockInputStream.h>
#include <Storages/StorageBuffer.h>
#include <Storages/StorageFactory.h>
#include <Storages/AlterCommands.h>
#include <Parsers/ASTInsertQuery.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTExpressionList.h>
#include <Common/CurrentMetrics.h>
#include <Common/MemoryTracker.h>
#include <Common/FieldVisitors.h>
#include <Common/quoteString.h>
#include <Common/typeid_cast.h>
#include <Common/ProfileEvents.h>
#include <common/logger_useful.h>
#include <common/getThreadId.h>
#include <ext/range.h>
#include <Processors/QueryPlan/ExpressionStep.h>
#include <Processors/Transforms/FilterTransform.h>
#include <Processors/Transforms/ExpressionTransform.h>
#include <Processors/Sources/SourceFromInputStream.h>
#include <Processors/QueryPlan/SettingQuotaAndLimitsStep.h>
#include <Processors/QueryPlan/ReadFromPreparedSource.h>
#include <Processors/QueryPlan/UnionStep.h>
namespace ProfileEvents
{
extern const Event StorageBufferFlush;
extern const Event StorageBufferErrorOnFlush;
extern const Event StorageBufferPassedAllMinThresholds;
extern const Event StorageBufferPassedTimeMaxThreshold;
extern const Event StorageBufferPassedRowsMaxThreshold;
extern const Event StorageBufferPassedBytesMaxThreshold;
}
namespace CurrentMetrics
{
extern const Metric StorageBufferRows;
extern const Metric StorageBufferBytes;
}
namespace DB
{
namespace ErrorCodes
{
extern const int BAD_ARGUMENTS;
extern const int NOT_IMPLEMENTED;
extern const int LOGICAL_ERROR;
extern const int INFINITE_LOOP;
extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
}
StorageBuffer::StorageBuffer(
const StorageID & table_id_,
const ColumnsDescription & columns_,
const ConstraintsDescription & constraints_,
const Context & context_,
size_t num_shards_,
const Thresholds & min_thresholds_,
const Thresholds & max_thresholds_,
const StorageID & destination_id_,
bool allow_materialized_)
: IStorage(table_id_)
, global_context(context_.getGlobalContext())
, num_shards(num_shards_), buffers(num_shards_)
, min_thresholds(min_thresholds_)
, max_thresholds(max_thresholds_)
, destination_id(destination_id_)
, allow_materialized(allow_materialized_)
, log(&Poco::Logger::get("StorageBuffer (" + table_id_.getFullTableName() + ")"))
, bg_pool(global_context.getBufferFlushSchedulePool())
{
StorageInMemoryMetadata storage_metadata;
storage_metadata.setColumns(columns_);
storage_metadata.setConstraints(constraints_);
setInMemoryMetadata(storage_metadata);
}
/// Reads from one buffer (from one block) under its mutex.
class BufferSource : public SourceWithProgress
{
public:
BufferSource(const Names & column_names_, StorageBuffer::Buffer & buffer_, const StorageBuffer & storage, const StorageMetadataPtr & metadata_snapshot)
: SourceWithProgress(
metadata_snapshot->getSampleBlockForColumns(column_names_, storage.getVirtuals(), storage.getStorageID()))
, column_names_and_types(metadata_snapshot->getColumns().getAllWithSubcolumns().addTypes(column_names_))
, buffer(buffer_) {}
String getName() const override { return "Buffer"; }
protected:
Chunk generate() override
{
Chunk res;
if (has_been_read)
return res;
has_been_read = true;
std::lock_guard lock(buffer.mutex);
if (!buffer.data.rows())
return res;
Columns columns;
columns.reserve(column_names_and_types.size());
for (const auto & elem : column_names_and_types)
{
const auto & current_column = buffer.data.getByName(elem.getNameInStorage()).column;
if (elem.isSubcolumn())
columns.emplace_back(elem.getTypeInStorage()->getSubcolumn(elem.getSubcolumnName(), *current_column));
else
columns.emplace_back(std::move(current_column));
}
UInt64 size = columns.at(0)->size();
res.setColumns(std::move(columns), size);
return res;
}
private:
NamesAndTypesList column_names_and_types;
StorageBuffer::Buffer & buffer;
bool has_been_read = false;
};
QueryProcessingStage::Enum StorageBuffer::getQueryProcessingStage(const Context & context, QueryProcessingStage::Enum to_stage, SelectQueryInfo & query_info) const
{
if (destination_id)
{
auto destination = DatabaseCatalog::instance().getTable(destination_id, context);
if (destination.get() == this)
throw Exception("Destination table is myself. Read will cause infinite loop.", ErrorCodes::INFINITE_LOOP);
return destination->getQueryProcessingStage(context, to_stage, query_info);
}
return QueryProcessingStage::FetchColumns;
}
Pipe StorageBuffer::read(
const Names & column_names,
const StorageMetadataPtr & metadata_snapshot,
SelectQueryInfo & query_info,
const Context & context,
QueryProcessingStage::Enum processed_stage,
const size_t max_block_size,
const unsigned num_streams)
{
QueryPlan plan;
read(plan, column_names, metadata_snapshot, query_info, context, processed_stage, max_block_size, num_streams);
return plan.convertToPipe();
}
void StorageBuffer::read(
QueryPlan & query_plan,
const Names & column_names,
const StorageMetadataPtr & metadata_snapshot,
SelectQueryInfo & query_info,
const Context & context,
QueryProcessingStage::Enum processed_stage,
size_t max_block_size,
unsigned num_streams)
{
if (destination_id)
{
auto destination = DatabaseCatalog::instance().getTable(destination_id, context);
if (destination.get() == this)
throw Exception("Destination table is myself. Read will cause infinite loop.", ErrorCodes::INFINITE_LOOP);
auto destination_lock = destination->lockForShare(context.getCurrentQueryId(), context.getSettingsRef().lock_acquire_timeout);
auto destination_metadata_snapshot = destination->getInMemoryMetadataPtr();
const bool dst_has_same_structure = std::all_of(column_names.begin(), column_names.end(), [metadata_snapshot, destination_metadata_snapshot](const String& column_name)
{
const auto & dest_columns = destination_metadata_snapshot->getColumns();
const auto & our_columns = metadata_snapshot->getColumns();
return dest_columns.hasPhysicalOrSubcolumn(column_name) &&
dest_columns.getPhysicalOrSubcolumn(column_name).type->equals(*our_columns.getPhysicalOrSubcolumn(column_name).type);
});
if (dst_has_same_structure)
{
if (query_info.order_optimizer)
query_info.input_order_info = query_info.order_optimizer->getInputOrder(destination_metadata_snapshot, context);
/// The destination table has the same structure of the requested columns and we can simply read blocks from there.
destination->read(
query_plan, column_names, destination_metadata_snapshot, query_info,
context, processed_stage, max_block_size, num_streams);
}
else
{
/// There is a struct mismatch and we need to convert read blocks from the destination table.
const Block header = metadata_snapshot->getSampleBlock();
Names columns_intersection = column_names;
Block header_after_adding_defaults = header;
const auto & dest_columns = destination_metadata_snapshot->getColumns();
const auto & our_columns = metadata_snapshot->getColumns();
for (const String & column_name : column_names)
{
if (!dest_columns.hasPhysical(column_name))
{
LOG_WARNING(log, "Destination table {} doesn't have column {}. The default values are used.", destination_id.getNameForLogs(), backQuoteIfNeed(column_name));
boost::range::remove_erase(columns_intersection, column_name);
continue;
}
const auto & dst_col = dest_columns.getPhysical(column_name);
const auto & col = our_columns.getPhysical(column_name);
if (!dst_col.type->equals(*col.type))
{
LOG_WARNING(log, "Destination table {} has different type of column {} ({} != {}). Data from destination table are converted.", destination_id.getNameForLogs(), backQuoteIfNeed(column_name), dst_col.type->getName(), col.type->getName());
header_after_adding_defaults.getByName(column_name) = ColumnWithTypeAndName(dst_col.type, column_name);
}
}
if (columns_intersection.empty())
{
LOG_WARNING(log, "Destination table {} has no common columns with block in buffer. Block of data is skipped.", destination_id.getNameForLogs());
}
else
{
destination->read(
query_plan, columns_intersection, destination_metadata_snapshot, query_info,
context, processed_stage, max_block_size, num_streams);
if (query_plan.isInitialized())
{
auto adding_missed = std::make_unique<AddingMissedStep>(
query_plan.getCurrentDataStream(),
header_after_adding_defaults,
metadata_snapshot->getColumns(), context);
adding_missed->setStepDescription("Add columns missing in destination table");
query_plan.addStep(std::move(adding_missed));
auto actions_dag = ActionsDAG::makeConvertingActions(
query_plan.getCurrentDataStream().header.getColumnsWithTypeAndName(),
header.getColumnsWithTypeAndName(),
ActionsDAG::MatchColumnsMode::Name);
auto converting = std::make_unique<ExpressionStep>(query_plan.getCurrentDataStream(), actions_dag);
converting->setStepDescription("Convert destination table columns to Buffer table structure");
query_plan.addStep(std::move(converting));
}
}
}
if (query_plan.isInitialized())
{
StreamLocalLimits limits;
SizeLimits leaf_limits;
/// Add table lock for destination table.
auto adding_limits_and_quota = std::make_unique<SettingQuotaAndLimitsStep>(
query_plan.getCurrentDataStream(),
destination,
std::move(destination_lock),
limits,
leaf_limits,
nullptr,
nullptr);
adding_limits_and_quota->setStepDescription("Lock destination table for Buffer");
query_plan.addStep(std::move(adding_limits_and_quota));
}
}
Pipe pipe_from_buffers;
{
Pipes pipes_from_buffers;
pipes_from_buffers.reserve(num_shards);
for (auto & buf : buffers)
pipes_from_buffers.emplace_back(std::make_shared<BufferSource>(column_names, buf, *this, metadata_snapshot));
pipe_from_buffers = Pipe::unitePipes(std::move(pipes_from_buffers));
}
if (pipe_from_buffers.empty())
return;
QueryPlan buffers_plan;
/** If the sources from the table were processed before some non-initial stage of query execution,
* then sources from the buffers must also be wrapped in the processing pipeline before the same stage.
*/
if (processed_stage > QueryProcessingStage::FetchColumns)
{
auto interpreter = InterpreterSelectQuery(
query_info.query, context, std::move(pipe_from_buffers),
SelectQueryOptions(processed_stage));
interpreter.buildQueryPlan(buffers_plan);
}
else
{
if (query_info.prewhere_info)
{
pipe_from_buffers.addSimpleTransform([&](const Block & header)
{
return std::make_shared<FilterTransform>(
header, query_info.prewhere_info->prewhere_actions,
query_info.prewhere_info->prewhere_column_name, query_info.prewhere_info->remove_prewhere_column);
});
if (query_info.prewhere_info->alias_actions)
{
pipe_from_buffers.addSimpleTransform([&](const Block & header)
{
return std::make_shared<ExpressionTransform>(header, query_info.prewhere_info->alias_actions);
});
}
}
auto read_from_buffers = std::make_unique<ReadFromPreparedSource>(std::move(pipe_from_buffers));
read_from_buffers->setStepDescription("Read from buffers of Buffer table");
buffers_plan.addStep(std::move(read_from_buffers));
}
if (!query_plan.isInitialized())
{
query_plan = std::move(buffers_plan);
return;
}
auto result_header = buffers_plan.getCurrentDataStream().header;
/// Convert structure from table to structure from buffer.
if (!blocksHaveEqualStructure(query_plan.getCurrentDataStream().header, result_header))
{
auto convert_actions_dag = ActionsDAG::makeConvertingActions(
query_plan.getCurrentDataStream().header.getColumnsWithTypeAndName(),
result_header.getColumnsWithTypeAndName(),
ActionsDAG::MatchColumnsMode::Name);
auto converting = std::make_unique<ExpressionStep>(query_plan.getCurrentDataStream(), convert_actions_dag);
query_plan.addStep(std::move(converting));
}
DataStreams input_streams;
input_streams.emplace_back(query_plan.getCurrentDataStream());
input_streams.emplace_back(buffers_plan.getCurrentDataStream());
std::vector<std::unique_ptr<QueryPlan>> plans;
plans.emplace_back(std::make_unique<QueryPlan>(std::move(query_plan)));
plans.emplace_back(std::make_unique<QueryPlan>(std::move(buffers_plan)));
query_plan = QueryPlan();
auto union_step = std::make_unique<UnionStep>(std::move(input_streams), result_header);
union_step->setStepDescription("Unite sources from Buffer table");
query_plan.unitePlans(std::move(union_step), std::move(plans));
}
static void appendBlock(const Block & from, Block & to)
{
if (!to)
throw Exception("Cannot append to empty block", ErrorCodes::LOGICAL_ERROR);
assertBlocksHaveEqualStructure(from, to, "Buffer");
from.checkNumberOfRows();
to.checkNumberOfRows();
size_t rows = from.rows();
size_t bytes = from.bytes();
CurrentMetrics::add(CurrentMetrics::StorageBufferRows, rows);
CurrentMetrics::add(CurrentMetrics::StorageBufferBytes, bytes);
size_t old_rows = to.rows();
MutableColumnPtr last_col;
try
{
MemoryTracker::BlockerInThread temporarily_disable_memory_tracker;
for (size_t column_no = 0, columns = to.columns(); column_no < columns; ++column_no)
{
const IColumn & col_from = *from.getByPosition(column_no).column.get();
last_col = IColumn::mutate(std::move(to.getByPosition(column_no).column));
last_col->insertRangeFrom(col_from, 0, rows);
to.getByPosition(column_no).column = std::move(last_col);
}
}
catch (...)
{
/// Rollback changes.
/// In case of rollback, it is better to ignore memory limits instead of abnormal server termination.
/// So ignore any memory limits, even global (since memory tracking has drift).
MemoryTracker::BlockerInThread temporarily_ignore_any_memory_limits(VariableContext::Global);
try
{
for (size_t column_no = 0, columns = to.columns(); column_no < columns; ++column_no)
{
ColumnPtr & col_to = to.getByPosition(column_no).column;
/// If there is no column, then the exception was thrown in the middle of append, in the insertRangeFrom()
if (!col_to)
{
col_to = std::move(last_col);
/// Suppress clang-tidy [bugprone-use-after-move]
last_col = {};
}
/// But if there is still nothing, abort
if (!col_to)
throw Exception("No column to rollback", ErrorCodes::LOGICAL_ERROR);
if (col_to->size() != old_rows)
col_to = col_to->cut(0, old_rows);
}
}
catch (...)
{
/// In case when we cannot rollback, do not leave incorrect state in memory.
std::terminate();
}
throw;
}
}
class BufferBlockOutputStream : public IBlockOutputStream
{
public:
explicit BufferBlockOutputStream(
StorageBuffer & storage_,
const StorageMetadataPtr & metadata_snapshot_)
: storage(storage_)
, metadata_snapshot(metadata_snapshot_)
{}
Block getHeader() const override { return metadata_snapshot->getSampleBlock(); }
void write(const Block & block) override
{
if (!block)
return;
// Check table structure.
metadata_snapshot->check(block, true);
size_t rows = block.rows();
if (!rows)
return;
StoragePtr destination;
if (storage.destination_id)
{
destination = DatabaseCatalog::instance().tryGetTable(storage.destination_id, storage.global_context);
if (destination.get() == &storage)
throw Exception("Destination table is myself. Write will cause infinite loop.", ErrorCodes::INFINITE_LOOP);
}
size_t bytes = block.bytes();
storage.writes.rows += rows;
storage.writes.bytes += bytes;
/// If the block already exceeds the maximum limit, then we skip the buffer.
if (rows > storage.max_thresholds.rows || bytes > storage.max_thresholds.bytes)
{
if (storage.destination_id)
{
LOG_TRACE(storage.log, "Writing block with {} rows, {} bytes directly.", rows, bytes);
storage.writeBlockToDestination(block, destination);
}
return;
}
/// We distribute the load on the shards by the stream number.
const auto start_shard_num = getThreadId() % storage.num_shards;
/// We loop through the buffers, trying to lock mutex. No more than one lap.
auto shard_num = start_shard_num;
StorageBuffer::Buffer * least_busy_buffer = nullptr;
std::unique_lock<std::mutex> least_busy_lock;
size_t least_busy_shard_rows = 0;
for (size_t try_no = 0; try_no < storage.num_shards; ++try_no)
{
std::unique_lock lock(storage.buffers[shard_num].mutex, std::try_to_lock);
if (lock.owns_lock())
{
size_t num_rows = storage.buffers[shard_num].data.rows();
if (!least_busy_buffer || num_rows < least_busy_shard_rows)
{
least_busy_buffer = &storage.buffers[shard_num];
least_busy_lock = std::move(lock);
least_busy_shard_rows = num_rows;
}
}
shard_num = (shard_num + 1) % storage.num_shards;
}
/// If you still can not lock anything at once, then we'll wait on mutex.
if (!least_busy_buffer)
{
least_busy_buffer = &storage.buffers[start_shard_num];
least_busy_lock = std::unique_lock(least_busy_buffer->mutex);
}
insertIntoBuffer(block, *least_busy_buffer);
least_busy_lock.unlock();
storage.reschedule();
}
private:
StorageBuffer & storage;
StorageMetadataPtr metadata_snapshot;
void insertIntoBuffer(const Block & block, StorageBuffer::Buffer & buffer)
{
time_t current_time = time(nullptr);
/// Sort the columns in the block. This is necessary to make it easier to concatenate the blocks later.
Block sorted_block = block.sortColumns();
if (!buffer.data)
{
buffer.data = sorted_block.cloneEmpty();
}
else if (storage.checkThresholds(buffer, current_time, sorted_block.rows(), sorted_block.bytes()))
{
/** If, after inserting the buffer, the constraints are exceeded, then we will reset the buffer.
* This also protects against unlimited consumption of RAM, since if it is impossible to write to the table,
* an exception will be thrown, and new data will not be added to the buffer.
*/
storage.flushBuffer(buffer, false /* check_thresholds */, true /* locked */);
}
if (!buffer.first_write_time)
buffer.first_write_time = current_time;
appendBlock(sorted_block, buffer.data);
}
};
BlockOutputStreamPtr StorageBuffer::write(const ASTPtr & /*query*/, const StorageMetadataPtr & metadata_snapshot, const Context & /*context*/)
{
return std::make_shared<BufferBlockOutputStream>(*this, metadata_snapshot);
}
bool StorageBuffer::mayBenefitFromIndexForIn(
const ASTPtr & left_in_operand, const Context & query_context, const StorageMetadataPtr & /*metadata_snapshot*/) const
{
if (!destination_id)
return false;
auto destination = DatabaseCatalog::instance().getTable(destination_id, query_context);
if (destination.get() == this)
throw Exception("Destination table is myself. Read will cause infinite loop.", ErrorCodes::INFINITE_LOOP);
return destination->mayBenefitFromIndexForIn(left_in_operand, query_context, destination->getInMemoryMetadataPtr());
}
void StorageBuffer::startup()
{
if (global_context.getSettingsRef().readonly)
{
LOG_WARNING(log, "Storage {} is run with readonly settings, it will not be able to insert data. Set appropriate system_profile to fix this.", getName());
}
flush_handle = bg_pool.createTask(log->name() + "/Bg", [this]{ backgroundFlush(); });
flush_handle->activateAndSchedule();
}
void StorageBuffer::shutdown()
{
if (!flush_handle)
return;
flush_handle->deactivate();
try
{
optimize(nullptr /*query*/, getInMemoryMetadataPtr(), {} /*partition*/, false /*final*/, false /*deduplicate*/, {}, global_context);
}
catch (...)
{
tryLogCurrentException(__PRETTY_FUNCTION__);
}
}
/** NOTE If you do OPTIMIZE after insertion,
* it does not guarantee, that all data will be in destination table at the time of next SELECT just after OPTIMIZE.
*
* Because in case if there was already running flushBuffer method,
* then call to flushBuffer inside OPTIMIZE will see empty buffer and return quickly,
* but at the same time, the already running flushBuffer method possibly is not finished,
* so next SELECT will observe missing data.
*
* This kind of race condition make very hard to implement proper tests.
*/
bool StorageBuffer::optimize(
const ASTPtr & /*query*/,
const StorageMetadataPtr & /*metadata_snapshot*/,
const ASTPtr & partition,
bool final,
bool deduplicate,
const Names & /* deduplicate_by_columns */,
const Context & /*context*/)
{
if (partition)
throw Exception("Partition cannot be specified when optimizing table of type Buffer", ErrorCodes::NOT_IMPLEMENTED);
if (final)
throw Exception("FINAL cannot be specified when optimizing table of type Buffer", ErrorCodes::NOT_IMPLEMENTED);
if (deduplicate)
throw Exception("DEDUPLICATE cannot be specified when optimizing table of type Buffer", ErrorCodes::NOT_IMPLEMENTED);
flushAllBuffers(false, true);
return true;
}
bool StorageBuffer::checkThresholds(const Buffer & buffer, time_t current_time, size_t additional_rows, size_t additional_bytes) const
{
time_t time_passed = 0;
if (buffer.first_write_time)
time_passed = current_time - buffer.first_write_time;
size_t rows = buffer.data.rows() + additional_rows;
size_t bytes = buffer.data.bytes() + additional_bytes;
return checkThresholdsImpl(rows, bytes, time_passed);
}
bool StorageBuffer::checkThresholdsImpl(size_t rows, size_t bytes, time_t time_passed) const
{
if (time_passed > min_thresholds.time && rows > min_thresholds.rows && bytes > min_thresholds.bytes)
{
ProfileEvents::increment(ProfileEvents::StorageBufferPassedAllMinThresholds);
return true;
}
if (time_passed > max_thresholds.time)
{
ProfileEvents::increment(ProfileEvents::StorageBufferPassedTimeMaxThreshold);
return true;
}
if (rows > max_thresholds.rows)
{
ProfileEvents::increment(ProfileEvents::StorageBufferPassedRowsMaxThreshold);
return true;
}
if (bytes > max_thresholds.bytes)
{
ProfileEvents::increment(ProfileEvents::StorageBufferPassedBytesMaxThreshold);
return true;
}
return false;
}
void StorageBuffer::flushAllBuffers(bool check_thresholds, bool reset_blocks_structure)
{
for (auto & buf : buffers)
flushBuffer(buf, check_thresholds, false, reset_blocks_structure);
}
void StorageBuffer::flushBuffer(Buffer & buffer, bool check_thresholds, bool locked, bool reset_block_structure)
{
Block block_to_write;
time_t current_time = time(nullptr);
size_t rows = 0;
size_t bytes = 0;
time_t time_passed = 0;
std::unique_lock lock(buffer.mutex, std::defer_lock);
if (!locked)
lock.lock();
block_to_write = buffer.data.cloneEmpty();
rows = buffer.data.rows();
bytes = buffer.data.bytes();
if (buffer.first_write_time)
time_passed = current_time - buffer.first_write_time;
if (check_thresholds)
{
if (!checkThresholdsImpl(rows, bytes, time_passed))
return;
}
else
{
if (rows == 0)
return;
}
buffer.data.swap(block_to_write);
buffer.first_write_time = 0;
CurrentMetrics::sub(CurrentMetrics::StorageBufferRows, block_to_write.rows());
CurrentMetrics::sub(CurrentMetrics::StorageBufferBytes, block_to_write.bytes());
ProfileEvents::increment(ProfileEvents::StorageBufferFlush);
if (!destination_id)
{
LOG_TRACE(log, "Flushing buffer with {} rows (discarded), {} bytes, age {} seconds {}.", rows, bytes, time_passed, (check_thresholds ? "(bg)" : "(direct)"));
return;
}
/** For simplicity, buffer is locked during write.
* We could unlock buffer temporary, but it would lead to too many difficulties:
* - data, that is written, will not be visible for SELECTs;
* - new data could be appended to buffer, and in case of exception, we must merge it with old data, that has not been written;
* - this could lead to infinite memory growth.
*/
Stopwatch watch;
try
{
writeBlockToDestination(block_to_write, DatabaseCatalog::instance().tryGetTable(destination_id, global_context));
if (reset_block_structure)
buffer.data.clear();
}
catch (...)
{
ProfileEvents::increment(ProfileEvents::StorageBufferErrorOnFlush);
/// Return the block to its place in the buffer.
CurrentMetrics::add(CurrentMetrics::StorageBufferRows, block_to_write.rows());
CurrentMetrics::add(CurrentMetrics::StorageBufferBytes, block_to_write.bytes());
buffer.data.swap(block_to_write);
if (!buffer.first_write_time)
buffer.first_write_time = current_time;
/// After a while, the next write attempt will happen.
throw;
}
UInt64 milliseconds = watch.elapsedMilliseconds();
LOG_TRACE(log, "Flushing buffer with {} rows, {} bytes, age {} seconds, took {} ms {}.", rows, bytes, time_passed, milliseconds, (check_thresholds ? "(bg)" : "(direct)"));
}
void StorageBuffer::writeBlockToDestination(const Block & block, StoragePtr table)
{
if (!destination_id || !block)
return;
if (!table)
{
LOG_ERROR(log, "Destination table {} doesn't exist. Block of data is discarded.", destination_id.getNameForLogs());
return;
}
auto destination_metadata_snapshot = table->getInMemoryMetadataPtr();
MemoryTracker::BlockerInThread temporarily_disable_memory_tracker;
auto insert = std::make_shared<ASTInsertQuery>();
insert->table_id = destination_id;
/** We will insert columns that are the intersection set of columns of the buffer table and the subordinate table.
* This will support some of the cases (but not all) when the table structure does not match.
*/
Block structure_of_destination_table = allow_materialized ? destination_metadata_snapshot->getSampleBlock()
: destination_metadata_snapshot->getSampleBlockNonMaterialized();
Block block_to_write;
for (size_t i : ext::range(0, structure_of_destination_table.columns()))
{
auto dst_col = structure_of_destination_table.getByPosition(i);
if (block.has(dst_col.name))
{
auto column = block.getByName(dst_col.name);
if (!column.type->equals(*dst_col.type))
{
LOG_WARNING(log, "Destination table {} have different type of column {} ({} != {}). Block of data is converted.", destination_id.getNameForLogs(), backQuoteIfNeed(column.name), dst_col.type->getName(), column.type->getName());
column.column = castColumn(column, dst_col.type);
column.type = dst_col.type;
}
block_to_write.insert(column);
}
}
if (block_to_write.columns() == 0)
{
LOG_ERROR(log, "Destination table {} have no common columns with block in buffer. Block of data is discarded.", destination_id.getNameForLogs());
return;
}
if (block_to_write.columns() != block.columns())
LOG_WARNING(log, "Not all columns from block in buffer exist in destination table {}. Some columns are discarded.", destination_id.getNameForLogs());
auto list_of_columns = std::make_shared<ASTExpressionList>();
insert->columns = list_of_columns;
list_of_columns->children.reserve(block_to_write.columns());
for (const auto & column : block_to_write)
list_of_columns->children.push_back(std::make_shared<ASTIdentifier>(column.name));
auto insert_context = Context(global_context);
insert_context.makeQueryContext();
InterpreterInsertQuery interpreter{insert, insert_context, allow_materialized};
auto block_io = interpreter.execute();
block_io.out->writePrefix();
block_io.out->write(block_to_write);
block_io.out->writeSuffix();
}
void StorageBuffer::backgroundFlush()
{
try
{
flushAllBuffers(true);
}
catch (...)
{
tryLogCurrentException(__PRETTY_FUNCTION__);
}
reschedule();
}
void StorageBuffer::reschedule()
{
time_t min_first_write_time = std::numeric_limits<time_t>::max();
time_t rows = 0;
for (auto & buffer : buffers)
{
/// try_to_lock here to avoid waiting for other layers flushing to be finished,
/// since the buffer table may:
/// - push to Distributed table, that may take too much time,
/// - push to table with materialized views attached,
/// this is also may take some time.
///
/// try_to_lock is also ok for background flush, since if there is
/// INSERT contended, then the reschedule will be done after
/// INSERT will be done.
std::unique_lock lock(buffer.mutex, std::try_to_lock);
if (lock.owns_lock())
{
min_first_write_time = buffer.first_write_time;
rows += buffer.data.rows();
}
}
/// will be rescheduled via INSERT
if (!rows)
return;
time_t current_time = time(nullptr);
time_t time_passed = current_time - min_first_write_time;
size_t min = std::max<ssize_t>(min_thresholds.time - time_passed, 1);
size_t max = std::max<ssize_t>(max_thresholds.time - time_passed, 1);
flush_handle->scheduleAfter(std::min(min, max) * 1000);
}
void StorageBuffer::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const
{
for (const auto & command : commands)
{
if (command.type != AlterCommand::Type::ADD_COLUMN && command.type != AlterCommand::Type::MODIFY_COLUMN
&& command.type != AlterCommand::Type::DROP_COLUMN && command.type != AlterCommand::Type::COMMENT_COLUMN)
throw Exception(
"Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
ErrorCodes::NOT_IMPLEMENTED);
}
}
std::optional<UInt64> StorageBuffer::totalRows(const Settings & settings) const
{
std::optional<UInt64> underlying_rows;
auto underlying = DatabaseCatalog::instance().tryGetTable(destination_id, global_context);
if (underlying)
underlying_rows = underlying->totalRows(settings);
if (!underlying_rows)
return underlying_rows;
UInt64 rows = 0;
for (const auto & buffer : buffers)
{
std::lock_guard lock(buffer.mutex);
rows += buffer.data.rows();
}
return rows + *underlying_rows;
}
std::optional<UInt64> StorageBuffer::totalBytes(const Settings & /*settings*/) const
{
UInt64 bytes = 0;
for (const auto & buffer : buffers)
{
std::lock_guard lock(buffer.mutex);
bytes += buffer.data.allocatedBytes();
}
return bytes;
}
void StorageBuffer::alter(const AlterCommands & params, const Context & context, TableLockHolder &)
{
auto table_id = getStorageID();
checkAlterIsPossible(params, context.getSettingsRef());
auto metadata_snapshot = getInMemoryMetadataPtr();
/// Flush all buffers to storages, so that no non-empty blocks of the old
/// structure remain. Structure of empty blocks will be updated during first
/// insert.
optimize({} /*query*/, metadata_snapshot, {} /*partition_id*/, false /*final*/, false /*deduplicate*/, {}, context);
StorageInMemoryMetadata new_metadata = *metadata_snapshot;
params.apply(new_metadata, context);
DatabaseCatalog::instance().getDatabase(table_id.database_name)->alterTable(context, table_id, new_metadata);
setInMemoryMetadata(new_metadata);
}
void registerStorageBuffer(StorageFactory & factory)
{
/** Buffer(db, table, num_buckets, min_time, max_time, min_rows, max_rows, min_bytes, max_bytes)
*
* db, table - in which table to put data from buffer.
* num_buckets - level of parallelism.
* min_time, max_time, min_rows, max_rows, min_bytes, max_bytes - conditions for flushing the buffer.
*/
factory.registerStorage("Buffer", [](const StorageFactory::Arguments & args)
{
ASTs & engine_args = args.engine_args;
if (engine_args.size() != 9)
throw Exception("Storage Buffer requires 9 parameters: "
" destination_database, destination_table, num_buckets, min_time, max_time, min_rows, max_rows, min_bytes, max_bytes.",
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
// Table and database name arguments accept expressions, evaluate them.
engine_args[0] = evaluateConstantExpressionForDatabaseName(engine_args[0], args.local_context);
engine_args[1] = evaluateConstantExpressionOrIdentifierAsLiteral(engine_args[1], args.local_context);
// After we evaluated all expressions, check that all arguments are
// literals.
for (size_t i = 0; i < 9; i++)
{
if (!typeid_cast<ASTLiteral *>(engine_args[i].get()))
{
throw Exception(ErrorCodes::BAD_ARGUMENTS,
"Storage Buffer expects a literal as an argument #{}, got '{}'"
" instead", i, engine_args[i]->formatForErrorMessage());
}
}
String destination_database = engine_args[0]->as<ASTLiteral &>().value.safeGet<String>();
String destination_table = engine_args[1]->as<ASTLiteral &>().value.safeGet<String>();
UInt64 num_buckets = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), engine_args[2]->as<ASTLiteral &>().value);
Int64 min_time = applyVisitor(FieldVisitorConvertToNumber<Int64>(), engine_args[3]->as<ASTLiteral &>().value);
Int64 max_time = applyVisitor(FieldVisitorConvertToNumber<Int64>(), engine_args[4]->as<ASTLiteral &>().value);
UInt64 min_rows = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), engine_args[5]->as<ASTLiteral &>().value);
UInt64 max_rows = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), engine_args[6]->as<ASTLiteral &>().value);
UInt64 min_bytes = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), engine_args[7]->as<ASTLiteral &>().value);
UInt64 max_bytes = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), engine_args[8]->as<ASTLiteral &>().value);
/// If destination_id is not set, do not write data from the buffer, but simply empty the buffer.
StorageID destination_id = StorageID::createEmpty();
if (!destination_table.empty())
{
destination_id.database_name = args.context.resolveDatabase(destination_database);
destination_id.table_name = destination_table;
}
return StorageBuffer::create(
args.table_id,
args.columns,
args.constraints,
args.context,
num_buckets,
StorageBuffer::Thresholds{min_time, min_rows, min_bytes},
StorageBuffer::Thresholds{max_time, max_rows, max_bytes},
destination_id,
static_cast<bool>(args.local_context.getSettingsRef().insert_allow_materialized_columns));
},
{
.supports_parallel_insert = true,
});
}
}
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