ClickHouse/dbms/Dictionaries/CacheDictionary.cpp

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#include "CacheDictionary.h"
#include <functional>
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#include <memory>
#include <Columns/ColumnString.h>
#include <Common/BitHelpers.h>
#include <Common/CurrentMetrics.h>
#include <Common/HashTable/Hash.h>
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#include <Common/ProfileEvents.h>
#include <Common/ProfilingScopedRWLock.h>
#include <Common/randomSeed.h>
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#include <Common/typeid_cast.h>
#include <ext/range.h>
#include <ext/size.h>
#include <Common/setThreadName.h>
#include "CacheDictionary.inc.h"
#include "DictionaryBlockInputStream.h"
#include "DictionaryFactory.h"
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namespace ProfileEvents
{
extern const Event DictCacheKeysRequested;
extern const Event DictCacheKeysRequestedMiss;
extern const Event DictCacheKeysRequestedFound;
extern const Event DictCacheKeysExpired;
extern const Event DictCacheKeysNotFound;
extern const Event DictCacheKeysHit;
extern const Event DictCacheRequestTimeNs;
extern const Event DictCacheRequests;
extern const Event DictCacheLockWriteNs;
extern const Event DictCacheLockReadNs;
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}
namespace CurrentMetrics
{
extern const Metric DictCacheRequests;
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}
namespace DB
{
namespace ErrorCodes
{
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extern const int CACHE_DICTIONARY_UPDATE_FAIL;
extern const int TYPE_MISMATCH;
extern const int BAD_ARGUMENTS;
extern const int UNSUPPORTED_METHOD;
extern const int TOO_SMALL_BUFFER_SIZE;
}
inline size_t CacheDictionary::getCellIdx(const Key id) const
{
const auto hash = intHash64(id);
const auto idx = hash & size_overlap_mask;
return idx;
}
CacheDictionary::CacheDictionary(
const std::string & database_,
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const std::string & name_,
const DictionaryStructure & dict_struct_,
DictionarySourcePtr source_ptr_,
DictionaryLifetime dict_lifetime_,
size_t size_,
bool allow_read_expired_keys_,
size_t max_update_queue_size_,
size_t update_queue_push_timeout_milliseconds_,
size_t max_threads_for_updates_)
: database(database_)
, name(name_)
, full_name{database_.empty() ? name_ : (database_ + "." + name_)}
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, dict_struct(dict_struct_)
, source_ptr{std::move(source_ptr_)}
, dict_lifetime(dict_lifetime_)
, allow_read_expired_keys(allow_read_expired_keys_)
, max_update_queue_size(max_update_queue_size_)
, update_queue_push_timeout_milliseconds(update_queue_push_timeout_milliseconds_)
, max_threads_for_updates(max_threads_for_updates_)
, log(&Logger::get("ExternalDictionaries"))
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, size{roundUpToPowerOfTwoOrZero(std::max(size_, size_t(max_collision_length)))}
, size_overlap_mask{this->size - 1}
, cells{this->size}
, rnd_engine(randomSeed())
, update_queue(max_update_queue_size_)
, update_pool(max_threads_for_updates)
{
if (!this->source_ptr->supportsSelectiveLoad())
throw Exception{full_name + ": source cannot be used with CacheDictionary", ErrorCodes::UNSUPPORTED_METHOD};
createAttributes();
for (size_t i = 0; i < max_threads_for_updates; ++i)
update_pool.scheduleOrThrowOnError([this] { updateThreadFunction(); });
}
CacheDictionary::~CacheDictionary()
{
finished = true;
update_queue.clear();
for (size_t i = 0; i < max_threads_for_updates; ++i)
{
auto empty_finishing_ptr = std::make_shared<UpdateUnit>(std::vector<Key>());
update_queue.push(empty_finishing_ptr);
}
update_pool.wait();
}
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void CacheDictionary::toParent(const PaddedPODArray<Key> & ids, PaddedPODArray<Key> & out) const
{
const auto null_value = std::get<UInt64>(hierarchical_attribute->null_values);
getItemsNumberImpl<UInt64, UInt64>(*hierarchical_attribute, ids, out, [&](const size_t) { return null_value; });
}
/// Allow to use single value in same way as array.
static inline CacheDictionary::Key getAt(const PaddedPODArray<CacheDictionary::Key> & arr, const size_t idx)
{
return arr[idx];
}
static inline CacheDictionary::Key getAt(const CacheDictionary::Key & value, const size_t)
{
return value;
}
template <typename AncestorType>
void CacheDictionary::isInImpl(const PaddedPODArray<Key> & child_ids, const AncestorType & ancestor_ids, PaddedPODArray<UInt8> & out) const
{
/// Transform all children to parents until ancestor id or null_value will be reached.
size_t out_size = out.size();
memset(out.data(), 0xFF, out_size); /// 0xFF means "not calculated"
const auto null_value = std::get<UInt64>(hierarchical_attribute->null_values);
PaddedPODArray<Key> children(out_size, 0);
PaddedPODArray<Key> parents(child_ids.begin(), child_ids.end());
while (true)
{
size_t out_idx = 0;
size_t parents_idx = 0;
size_t new_children_idx = 0;
while (out_idx < out_size)
{
/// Already calculated
if (out[out_idx] != 0xFF)
{
++out_idx;
continue;
}
/// No parent
if (parents[parents_idx] == null_value)
{
out[out_idx] = 0;
}
/// Found ancestor
else if (parents[parents_idx] == getAt(ancestor_ids, parents_idx))
{
out[out_idx] = 1;
}
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/// Loop detected
else if (children[new_children_idx] == parents[parents_idx])
{
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out[out_idx] = 1;
}
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/// Found intermediate parent, add this value to search at next loop iteration
else
{
children[new_children_idx] = parents[parents_idx];
++new_children_idx;
}
++out_idx;
++parents_idx;
}
if (new_children_idx == 0)
break;
/// Transform all children to its parents.
children.resize(new_children_idx);
parents.resize(new_children_idx);
toParent(children, parents);
}
}
void CacheDictionary::isInVectorVector(
const PaddedPODArray<Key> & child_ids, const PaddedPODArray<Key> & ancestor_ids, PaddedPODArray<UInt8> & out) const
{
isInImpl(child_ids, ancestor_ids, out);
}
void CacheDictionary::isInVectorConstant(const PaddedPODArray<Key> & child_ids, const Key ancestor_id, PaddedPODArray<UInt8> & out) const
{
isInImpl(child_ids, ancestor_id, out);
}
void CacheDictionary::isInConstantVector(const Key child_id, const PaddedPODArray<Key> & ancestor_ids, PaddedPODArray<UInt8> & out) const
{
/// Special case with single child value.
const auto null_value = std::get<UInt64>(hierarchical_attribute->null_values);
PaddedPODArray<Key> child(1, child_id);
PaddedPODArray<Key> parent(1);
std::vector<Key> ancestors(1, child_id);
/// Iteratively find all ancestors for child.
while (true)
{
toParent(child, parent);
if (parent[0] == null_value)
break;
child[0] = parent[0];
ancestors.push_back(parent[0]);
}
/// Assuming short hierarchy, so linear search is Ok.
for (size_t i = 0, out_size = out.size(); i < out_size; ++i)
out[i] = std::find(ancestors.begin(), ancestors.end(), ancestor_ids[i]) != ancestors.end();
}
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void CacheDictionary::getString(const std::string & attribute_name, const PaddedPODArray<Key> & ids, ColumnString * out) const
{
auto & attribute = getAttribute(attribute_name);
checkAttributeType(full_name, attribute_name, attribute.type, AttributeUnderlyingType::utString);
const auto null_value = StringRef{std::get<String>(attribute.null_values)};
getItemsString(attribute, ids, out, [&](const size_t) { return null_value; });
}
void CacheDictionary::getString(
const std::string & attribute_name, const PaddedPODArray<Key> & ids, const ColumnString * const def, ColumnString * const out) const
{
auto & attribute = getAttribute(attribute_name);
checkAttributeType(full_name, attribute_name, attribute.type, AttributeUnderlyingType::utString);
getItemsString(attribute, ids, out, [&](const size_t row) { return def->getDataAt(row); });
}
void CacheDictionary::getString(
const std::string & attribute_name, const PaddedPODArray<Key> & ids, const String & def, ColumnString * const out) const
{
auto & attribute = getAttribute(attribute_name);
checkAttributeType(full_name, attribute_name, attribute.type, AttributeUnderlyingType::utString);
getItemsString(attribute, ids, out, [&](const size_t) { return StringRef{def}; });
}
/// returns cell_idx (always valid for replacing), 'cell is valid' flag, 'cell is outdated' flag
/// true false found and valid
/// false true not found (something outdated, maybe our cell)
/// false false not found (other id stored with valid data)
/// true true impossible
///
/// todo: split this func to two: find_for_get and find_for_set
CacheDictionary::FindResult CacheDictionary::findCellIdx(const Key & id, const CellMetadata::time_point_t now) const
{
auto pos = getCellIdx(id);
auto oldest_id = pos;
auto oldest_time = CellMetadata::time_point_t::max();
const auto stop = pos + max_collision_length;
for (; pos < stop; ++pos)
{
const auto cell_idx = pos & size_overlap_mask;
const auto & cell = cells[cell_idx];
if (cell.id != id)
{
/// maybe we already found nearest expired cell (try minimize collision_length on insert)
if (oldest_time > now && oldest_time > cell.expiresAt())
{
oldest_time = cell.expiresAt();
oldest_id = cell_idx;
}
continue;
}
if (cell.expiresAt() < now)
{
return {cell_idx, false, true};
}
return {cell_idx, true, false};
}
return {oldest_id, false, false};
}
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void CacheDictionary::has(const PaddedPODArray<Key> & ids, PaddedPODArray<UInt8> & out) const
{
/// There are three types of ids.
/// - Valid ids. These ids are presented in local cache and their lifetime is not expired.
/// - CacheExpired ids. Ids that are in local cache, but their values are rotted (lifetime is expired).
/// - CacheNotFound ids. We have to go to external storage to know its value.
/// Mapping: <id> -> { all indices `i` of `ids` such that `ids[i]` = <id> }
std::unordered_map<Key, std::vector<size_t>> cache_expired_ids;
std::unordered_map<Key, std::vector<size_t>> cache_not_found_ids;
size_t cache_hit = 0;
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const auto rows = ext::size(ids);
{
const ProfilingScopedReadRWLock read_lock{rw_lock, ProfileEvents::DictCacheLockReadNs};
const auto now = std::chrono::system_clock::now();
/// fetch up-to-date values, decide which ones require update
for (const auto row : ext::range(0, rows))
{
const auto id = ids[row];
const auto find_result = findCellIdx(id, now);
const auto & cell_idx = find_result.cell_idx;
auto insert_to_answer_routine = [&] ()
{
out[row] = !cells[cell_idx].isDefault();
};
if (!find_result.valid)
{
if (find_result.outdated)
{
cache_expired_ids[id].push_back(row);
if (allow_read_expired_keys)
insert_to_answer_routine();
}
else
{
cache_not_found_ids[id].push_back(row);
}
}
else
{
++cache_hit;
insert_to_answer_routine();
}
}
}
ProfileEvents::increment(ProfileEvents::DictCacheKeysExpired, cache_expired_ids.size());
ProfileEvents::increment(ProfileEvents::DictCacheKeysNotFound, cache_not_found_ids.size());
ProfileEvents::increment(ProfileEvents::DictCacheKeysHit, cache_hit);
query_count.fetch_add(rows, std::memory_order_relaxed);
hit_count.fetch_add(rows - cache_expired_ids.size() - cache_not_found_ids.size(), std::memory_order_release);
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if (cache_not_found_ids.empty())
{
/// Nothing to update - return;
if (cache_expired_ids.empty())
return;
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if (allow_read_expired_keys)
{
std::vector<Key> required_expired_ids;
required_expired_ids.reserve(cache_expired_ids.size());
std::transform(
std::begin(cache_expired_ids), std::end(cache_expired_ids),
std::back_inserter(required_expired_ids), [](auto & pair) { return pair.first; });
/// Callbacks are empty because we don't want to receive them after an unknown period of time.
auto update_unit_ptr = std::make_shared<UpdateUnit>(required_expired_ids);
tryPushToUpdateQueueOrThrow(update_unit_ptr);
/// Update is async - no need to wait.
return;
}
}
/// At this point we have two situations.
/// There may be both types of keys: cache_expired_ids and cache_not_found_ids.
/// We will update them all synchronously.
std::vector<Key> required_ids;
required_ids.reserve(cache_not_found_ids.size() + cache_expired_ids.size());
std::transform(
std::begin(cache_not_found_ids), std::end(cache_not_found_ids),
std::back_inserter(required_ids), [](auto & pair) { return pair.first; });
std::transform(
std::begin(cache_expired_ids), std::end(cache_expired_ids),
std::back_inserter(required_ids), [](auto & pair) { return pair.first; });
auto on_cell_updated = [&] (const Key id, const size_t)
{
for (const auto row : cache_not_found_ids[id])
out[row] = true;
for (const auto row : cache_expired_ids[id])
out[row] = true;
};
auto on_id_not_found = [&] (const Key id, const size_t)
{
for (const auto row : cache_not_found_ids[id])
out[row] = false;
for (const auto row : cache_expired_ids[id])
out[row] = true;
};
auto update_unit_ptr = std::make_shared<UpdateUnit>(required_ids, on_cell_updated, on_id_not_found);
tryPushToUpdateQueueOrThrow(update_unit_ptr);
waitForCurrentUpdateFinish(update_unit_ptr);
}
void CacheDictionary::createAttributes()
{
const auto attributes_size = dict_struct.attributes.size();
attributes.reserve(attributes_size);
bytes_allocated += size * sizeof(CellMetadata);
bytes_allocated += attributes_size * sizeof(attributes.front());
for (const auto & attribute : dict_struct.attributes)
{
attribute_index_by_name.emplace(attribute.name, attributes.size());
attributes.push_back(createAttributeWithType(attribute.underlying_type, attribute.null_value));
if (attribute.hierarchical)
{
hierarchical_attribute = &attributes.back();
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if (hierarchical_attribute->type != AttributeUnderlyingType::utUInt64)
throw Exception{full_name + ": hierarchical attribute must be UInt64.", ErrorCodes::TYPE_MISMATCH};
}
}
}
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CacheDictionary::Attribute CacheDictionary::createAttributeWithType(const AttributeUnderlyingType type, const Field & null_value)
{
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Attribute attr{type, {}, {}};
switch (type)
{
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#define DISPATCH(TYPE) \
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case AttributeUnderlyingType::ut##TYPE: \
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attr.null_values = TYPE(null_value.get<NearestFieldType<TYPE>>()); /* NOLINT */ \
attr.arrays = std::make_unique<ContainerType<TYPE>>(size); /* NOLINT */ \
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bytes_allocated += size * sizeof(TYPE); \
break;
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DISPATCH(UInt8)
DISPATCH(UInt16)
DISPATCH(UInt32)
DISPATCH(UInt64)
DISPATCH(UInt128)
DISPATCH(Int8)
DISPATCH(Int16)
DISPATCH(Int32)
DISPATCH(Int64)
DISPATCH(Decimal32)
DISPATCH(Decimal64)
DISPATCH(Decimal128)
DISPATCH(Float32)
DISPATCH(Float64)
#undef DISPATCH
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case AttributeUnderlyingType::utString:
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attr.null_values = null_value.get<String>();
attr.arrays = std::make_unique<ContainerType<StringRef>>(size);
bytes_allocated += size * sizeof(StringRef);
if (!string_arena)
string_arena = std::make_unique<ArenaWithFreeLists>();
break;
}
return attr;
}
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void CacheDictionary::setDefaultAttributeValue(Attribute & attribute, const Key idx) const
{
switch (attribute.type)
{
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case AttributeUnderlyingType::utUInt8:
std::get<ContainerPtrType<UInt8>>(attribute.arrays)[idx] = std::get<UInt8>(attribute.null_values);
break;
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case AttributeUnderlyingType::utUInt16:
std::get<ContainerPtrType<UInt16>>(attribute.arrays)[idx] = std::get<UInt16>(attribute.null_values);
break;
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case AttributeUnderlyingType::utUInt32:
std::get<ContainerPtrType<UInt32>>(attribute.arrays)[idx] = std::get<UInt32>(attribute.null_values);
break;
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case AttributeUnderlyingType::utUInt64:
std::get<ContainerPtrType<UInt64>>(attribute.arrays)[idx] = std::get<UInt64>(attribute.null_values);
break;
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case AttributeUnderlyingType::utUInt128:
std::get<ContainerPtrType<UInt128>>(attribute.arrays)[idx] = std::get<UInt128>(attribute.null_values);
break;
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case AttributeUnderlyingType::utInt8:
std::get<ContainerPtrType<Int8>>(attribute.arrays)[idx] = std::get<Int8>(attribute.null_values);
break;
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case AttributeUnderlyingType::utInt16:
std::get<ContainerPtrType<Int16>>(attribute.arrays)[idx] = std::get<Int16>(attribute.null_values);
break;
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case AttributeUnderlyingType::utInt32:
std::get<ContainerPtrType<Int32>>(attribute.arrays)[idx] = std::get<Int32>(attribute.null_values);
break;
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case AttributeUnderlyingType::utInt64:
std::get<ContainerPtrType<Int64>>(attribute.arrays)[idx] = std::get<Int64>(attribute.null_values);
break;
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case AttributeUnderlyingType::utFloat32:
std::get<ContainerPtrType<Float32>>(attribute.arrays)[idx] = std::get<Float32>(attribute.null_values);
break;
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case AttributeUnderlyingType::utFloat64:
std::get<ContainerPtrType<Float64>>(attribute.arrays)[idx] = std::get<Float64>(attribute.null_values);
break;
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case AttributeUnderlyingType::utDecimal32:
std::get<ContainerPtrType<Decimal32>>(attribute.arrays)[idx] = std::get<Decimal32>(attribute.null_values);
break;
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case AttributeUnderlyingType::utDecimal64:
std::get<ContainerPtrType<Decimal64>>(attribute.arrays)[idx] = std::get<Decimal64>(attribute.null_values);
break;
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case AttributeUnderlyingType::utDecimal128:
std::get<ContainerPtrType<Decimal128>>(attribute.arrays)[idx] = std::get<Decimal128>(attribute.null_values);
break;
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case AttributeUnderlyingType::utString:
{
const auto & null_value_ref = std::get<String>(attribute.null_values);
auto & string_ref = std::get<ContainerPtrType<StringRef>>(attribute.arrays)[idx];
if (string_ref.data != null_value_ref.data())
{
if (string_ref.data)
string_arena->free(const_cast<char *>(string_ref.data), string_ref.size);
string_ref = StringRef{null_value_ref};
}
break;
}
}
}
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void CacheDictionary::setAttributeValue(Attribute & attribute, const Key idx, const Field & value) const
{
switch (attribute.type)
{
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case AttributeUnderlyingType::utUInt8:
std::get<ContainerPtrType<UInt8>>(attribute.arrays)[idx] = value.get<UInt64>();
break;
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case AttributeUnderlyingType::utUInt16:
std::get<ContainerPtrType<UInt16>>(attribute.arrays)[idx] = value.get<UInt64>();
break;
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case AttributeUnderlyingType::utUInt32:
std::get<ContainerPtrType<UInt32>>(attribute.arrays)[idx] = value.get<UInt64>();
break;
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case AttributeUnderlyingType::utUInt64:
std::get<ContainerPtrType<UInt64>>(attribute.arrays)[idx] = value.get<UInt64>();
break;
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case AttributeUnderlyingType::utUInt128:
std::get<ContainerPtrType<UInt128>>(attribute.arrays)[idx] = value.get<UInt128>();
break;
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case AttributeUnderlyingType::utInt8:
std::get<ContainerPtrType<Int8>>(attribute.arrays)[idx] = value.get<Int64>();
break;
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case AttributeUnderlyingType::utInt16:
std::get<ContainerPtrType<Int16>>(attribute.arrays)[idx] = value.get<Int64>();
break;
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case AttributeUnderlyingType::utInt32:
std::get<ContainerPtrType<Int32>>(attribute.arrays)[idx] = value.get<Int64>();
break;
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case AttributeUnderlyingType::utInt64:
std::get<ContainerPtrType<Int64>>(attribute.arrays)[idx] = value.get<Int64>();
break;
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case AttributeUnderlyingType::utFloat32:
std::get<ContainerPtrType<Float32>>(attribute.arrays)[idx] = value.get<Float64>();
break;
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case AttributeUnderlyingType::utFloat64:
std::get<ContainerPtrType<Float64>>(attribute.arrays)[idx] = value.get<Float64>();
break;
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case AttributeUnderlyingType::utDecimal32:
std::get<ContainerPtrType<Decimal32>>(attribute.arrays)[idx] = value.get<Decimal32>();
break;
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case AttributeUnderlyingType::utDecimal64:
std::get<ContainerPtrType<Decimal64>>(attribute.arrays)[idx] = value.get<Decimal64>();
break;
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case AttributeUnderlyingType::utDecimal128:
std::get<ContainerPtrType<Decimal128>>(attribute.arrays)[idx] = value.get<Decimal128>();
break;
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case AttributeUnderlyingType::utString:
{
const auto & string = value.get<String>();
auto & string_ref = std::get<ContainerPtrType<StringRef>>(attribute.arrays)[idx];
const auto & null_value_ref = std::get<String>(attribute.null_values);
/// free memory unless it points to a null_value
if (string_ref.data && string_ref.data != null_value_ref.data())
string_arena->free(const_cast<char *>(string_ref.data), string_ref.size);
const auto str_size = string.size();
if (str_size != 0)
{
auto string_ptr = string_arena->alloc(str_size + 1);
std::copy(string.data(), string.data() + str_size + 1, string_ptr);
string_ref = StringRef{string_ptr, str_size};
}
else
string_ref = {};
break;
}
}
}
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CacheDictionary::Attribute & CacheDictionary::getAttribute(const std::string & attribute_name) const
{
const auto it = attribute_index_by_name.find(attribute_name);
if (it == std::end(attribute_index_by_name))
throw Exception{full_name + ": no such attribute '" + attribute_name + "'", ErrorCodes::BAD_ARGUMENTS};
return attributes[it->second];
}
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bool CacheDictionary::isEmptyCell(const UInt64 idx) const
{
return (idx != zero_cell_idx && cells[idx].id == 0)
|| (cells[idx].data == ext::safe_bit_cast<CellMetadata::time_point_urep_t>(CellMetadata::time_point_t()));
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}
PaddedPODArray<CacheDictionary::Key> CacheDictionary::getCachedIds() const
{
const ProfilingScopedReadRWLock read_lock{rw_lock, ProfileEvents::DictCacheLockReadNs};
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PaddedPODArray<Key> array;
for (size_t idx = 0; idx < cells.size(); ++idx)
{
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auto & cell = cells[idx];
if (!isEmptyCell(idx) && !cells[idx].isDefault())
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{
array.push_back(cell.id);
}
}
return array;
}
BlockInputStreamPtr CacheDictionary::getBlockInputStream(const Names & column_names, size_t max_block_size) const
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{
using BlockInputStreamType = DictionaryBlockInputStream<CacheDictionary, Key>;
return std::make_shared<BlockInputStreamType>(shared_from_this(), max_block_size, getCachedIds(), column_names);
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}
std::exception_ptr CacheDictionary::getLastException() const
{
const ProfilingScopedReadRWLock read_lock{rw_lock, ProfileEvents::DictCacheLockReadNs};
return last_exception;
}
void registerDictionaryCache(DictionaryFactory & factory)
{
auto create_layout = [=](const std::string & full_name,
const DictionaryStructure & dict_struct,
const Poco::Util::AbstractConfiguration & config,
const std::string & config_prefix,
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DictionarySourcePtr source_ptr) -> DictionaryPtr
{
if (dict_struct.key)
throw Exception{"'key' is not supported for dictionary of layout 'cache'",
ErrorCodes::UNSUPPORTED_METHOD};
if (dict_struct.range_min || dict_struct.range_max)
throw Exception{full_name
+ ": elements .structure.range_min and .structure.range_max should be defined only "
"for a dictionary of layout 'range_hashed'",
ErrorCodes::BAD_ARGUMENTS};
const auto & layout_prefix = config_prefix + ".layout";
const size_t size = config.getUInt64(layout_prefix + ".cache.size_in_cells");
if (size == 0)
throw Exception{full_name + ": dictionary of layout 'cache' cannot have 0 cells",
ErrorCodes::TOO_SMALL_BUFFER_SIZE};
const bool require_nonempty = config.getBool(config_prefix + ".require_nonempty", false);
if (require_nonempty)
throw Exception{full_name + ": dictionary of layout 'cache' cannot have 'require_nonempty' attribute set",
ErrorCodes::BAD_ARGUMENTS};
const String database = config.getString(config_prefix + ".database", "");
const String name = config.getString(config_prefix + ".name");
const DictionaryLifetime dict_lifetime{config, config_prefix + ".lifetime"};
const size_t max_update_queue_size =
config.getUInt64(layout_prefix + ".cache.max_update_queue_size", 100000);
if (max_update_queue_size == 0)
throw Exception{name + ": dictionary of layout 'cache' cannot have empty update queue of size 0",
ErrorCodes::TOO_SMALL_BUFFER_SIZE};
const bool allow_read_expired_keys =
config.getBool(layout_prefix + ".cache.allow_read_expired_keys", false);
const size_t update_queue_push_timeout_milliseconds =
config.getUInt64(layout_prefix + ".cache.update_queue_push_timeout_milliseconds", 10);
if (update_queue_push_timeout_milliseconds < 10)
throw Exception{name + ": dictionary of layout 'cache' have too little update_queue_push_timeout",
ErrorCodes::BAD_ARGUMENTS};
const size_t max_threads_for_updates =
config.getUInt64(layout_prefix + ".max_threads_for_updates", 4);
if (max_threads_for_updates == 0)
throw Exception{name + ": dictionary of layout 'cache' cannot have zero threads for updates.",
ErrorCodes::BAD_ARGUMENTS};
return std::make_unique<CacheDictionary>(
database, name, dict_struct, std::move(source_ptr), dict_lifetime, size,
allow_read_expired_keys, max_update_queue_size, update_queue_push_timeout_milliseconds,
max_threads_for_updates);
};
factory.registerLayout("cache", create_layout, false);
}
void CacheDictionary::updateThreadFunction()
{
setThreadName("AsyncUpdater");
while (!finished)
{
UpdateUnitPtr first_popped;
update_queue.pop(first_popped);
if (finished)
break;
/// Here we pop as many unit pointers from update queue as we can.
/// We fix current size to avoid livelock (or too long waiting),
/// when this thread pops from the queue and other threads push to the queue.
const size_t current_queue_size = update_queue.size();
if (current_queue_size > 0)
LOG_TRACE(log, "Performing bunch of keys update in cache dictionary with "
<< current_queue_size + 1 << " keys");
std::vector<UpdateUnitPtr> update_request;
update_request.reserve(current_queue_size + 1);
update_request.emplace_back(first_popped);
UpdateUnitPtr current_unit_ptr;
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while (!update_request.empty() && update_queue.tryPop(current_unit_ptr))
update_request.emplace_back(std::move(current_unit_ptr));
BunchUpdateUnit bunch_update_unit(update_request);
try
{
/// Update a bunch of ids.
update(bunch_update_unit);
/// Notify all threads about finished updating the bunch of ids
/// where their own ids were included.
std::unique_lock<std::mutex> lock(update_mutex);
for (auto & unit_ptr: update_request)
unit_ptr->is_done = true;
is_update_finished.notify_all();
}
catch (...)
{
std::unique_lock<std::mutex> lock(update_mutex);
/// It is a big trouble, because one bad query can make other threads fail with not relative exception.
/// So at this point all threads (and queries) will receive the same exception.
for (auto & unit_ptr: update_request)
unit_ptr->current_exception = std::current_exception();
is_update_finished.notify_all();
}
}
}
void CacheDictionary::waitForCurrentUpdateFinish(UpdateUnitPtr & update_unit_ptr) const
{
std::unique_lock<std::mutex> lock(update_mutex);
/*
* We wait here without any timeout to avoid SEGFAULT's.
* Consider timeout for wait had expired and main query's thread ended with exception
* or some other error. But the UpdateUnit with callbacks is left in the queue.
* It has these callback that capture god knows what from the current thread
* (most of the variables lies on the stack of finished thread) that
* intended to do a synchronous update. AsyncUpdate thread can touch deallocated memory and explode.
* */
is_update_finished.wait(
lock,
[&] {return update_unit_ptr->is_done || update_unit_ptr->current_exception; });
if (update_unit_ptr->current_exception)
std::rethrow_exception(update_unit_ptr->current_exception);
}
void CacheDictionary::tryPushToUpdateQueueOrThrow(UpdateUnitPtr & update_unit_ptr) const
{
if (!update_queue.tryPush(update_unit_ptr, update_queue_push_timeout_milliseconds))
throw DB::Exception(
"Cannot push to internal update queue in dictionary " + getFullName() + ". Timelimit of " +
std::to_string(update_queue_push_timeout_milliseconds) + " ms. exceeded. Current queue size is " +
std::to_string(update_queue.size()), ErrorCodes::CACHE_DICTIONARY_UPDATE_FAIL);
}
void CacheDictionary::update(BunchUpdateUnit & bunch_update_unit) const
{
CurrentMetrics::Increment metric_increment{CurrentMetrics::DictCacheRequests};
ProfileEvents::increment(ProfileEvents::DictCacheKeysRequested, bunch_update_unit.getRequestedIds().size());
std::unordered_map<Key, UInt8> remaining_ids{bunch_update_unit.getRequestedIds().size()};
for (const auto id : bunch_update_unit.getRequestedIds())
remaining_ids.insert({id, 0});
const auto now = std::chrono::system_clock::now();
/// Non const because it will be unlocked.
ProfilingScopedWriteRWLock write_lock{rw_lock, ProfileEvents::DictCacheLockWriteNs};
if (now > backoff_end_time.load())
{
try
{
if (error_count)
{
/// Recover after error: we have to clone the source here because
/// it could keep connections which should be reset after error.
source_ptr = source_ptr->clone();
}
Stopwatch watch;
/// To perform parallel loading.
BlockInputStreamPtr stream = nullptr;
{
ProfilingScopedWriteUnlocker unlocker(write_lock);
stream = source_ptr->loadIds(bunch_update_unit.getRequestedIds());
}
stream->readPrefix();
while (true)
{
Block block;
{
ProfilingScopedWriteUnlocker unlocker(write_lock);
block = stream->read();
if (!block)
break;
}
const auto id_column = typeid_cast<const ColumnUInt64 *>(block.safeGetByPosition(0).column.get());
if (!id_column)
throw Exception{name + ": id column has type different from UInt64.", ErrorCodes::TYPE_MISMATCH};
const auto & ids = id_column->getData();
/// cache column pointers
const auto column_ptrs = ext::map<std::vector>(
ext::range(0, attributes.size()), [&block](size_t i) { return block.safeGetByPosition(i + 1).column.get(); });
for (const auto i : ext::range(0, ids.size()))
{
const auto id = ids[i];
const auto find_result = findCellIdx(id, now);
const auto & cell_idx = find_result.cell_idx;
auto & cell = cells[cell_idx];
for (const auto attribute_idx : ext::range(0, attributes.size()))
{
const auto & attribute_column = *column_ptrs[attribute_idx];
auto & attribute = attributes[attribute_idx];
setAttributeValue(attribute, cell_idx, attribute_column[i]);
}
/// if cell id is zero and zero does not map to this cell, then the cell is unused
if (cell.id == 0 && cell_idx != zero_cell_idx)
element_count.fetch_add(1, std::memory_order_relaxed);
cell.id = id;
if (dict_lifetime.min_sec != 0 && dict_lifetime.max_sec != 0)
{
std::uniform_int_distribution<UInt64> distribution{dict_lifetime.min_sec, dict_lifetime.max_sec};
cell.setExpiresAt(now + std::chrono::seconds{distribution(rnd_engine)});
}
else
cell.setExpiresAt(std::chrono::time_point<std::chrono::system_clock>::max());
bunch_update_unit.informCallersAboutPresentId(id, cell_idx);
/// mark corresponding id as found
remaining_ids[id] = 1;
}
}
stream->readSuffix();
error_count = 0;
last_exception = std::exception_ptr{};
backoff_end_time = std::chrono::system_clock::time_point{};
ProfileEvents::increment(ProfileEvents::DictCacheRequestTimeNs, watch.elapsed());
}
catch (...)
{
++error_count;
last_exception = std::current_exception();
backoff_end_time = now + std::chrono::seconds(calculateDurationWithBackoff(rnd_engine, error_count));
tryLogException(last_exception, log, "Could not update cache dictionary '" + getFullName() +
"', next update is scheduled at " + ext::to_string(backoff_end_time.load()));
}
}
size_t not_found_num = 0, found_num = 0;
/// Check which ids have not been found and require setting null_value
for (const auto & id_found_pair : remaining_ids)
{
if (id_found_pair.second)
{
++found_num;
continue;
}
++not_found_num;
const auto id = id_found_pair.first;
const auto find_result = findCellIdx(id, now);
const auto & cell_idx = find_result.cell_idx;
auto & cell = cells[cell_idx];
if (error_count)
{
if (find_result.outdated)
{
/// We have expired data for that `id` so we can continue using it.
bool was_default = cell.isDefault();
cell.setExpiresAt(backoff_end_time);
if (was_default)
cell.setDefault();
if (was_default)
bunch_update_unit.informCallersAboutAbsentId(id, cell_idx);
else
bunch_update_unit.informCallersAboutPresentId(id, cell_idx);
continue;
}
/// We don't have expired data for that `id` so all we can do is to rethrow `last_exception`.
std::rethrow_exception(last_exception);
}
/// Check if cell had not been occupied before and increment element counter if it hadn't
if (cell.id == 0 && cell_idx != zero_cell_idx)
element_count.fetch_add(1, std::memory_order_relaxed);
cell.id = id;
if (dict_lifetime.min_sec != 0 && dict_lifetime.max_sec != 0)
{
std::uniform_int_distribution<UInt64> distribution{dict_lifetime.min_sec, dict_lifetime.max_sec};
cell.setExpiresAt(now + std::chrono::seconds{distribution(rnd_engine)});
}
else
cell.setExpiresAt(std::chrono::time_point<std::chrono::system_clock>::max());
/// Set null_value for each attribute
cell.setDefault();
for (auto & attribute : attributes)
setDefaultAttributeValue(attribute, cell_idx);
/// inform caller that the cell has not been found
bunch_update_unit.informCallersAboutAbsentId(id, cell_idx);
}
ProfileEvents::increment(ProfileEvents::DictCacheKeysRequestedMiss, not_found_num);
ProfileEvents::increment(ProfileEvents::DictCacheKeysRequestedFound, found_num);
ProfileEvents::increment(ProfileEvents::DictCacheRequests);
}
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}