ClickHouse/dbms/src/Common/ColumnsHashing.h
Alexander Kuzmenkov f3bde19b74 Do not use iterators in find() and emplace() methods of hash tables.
Instead, these methods return a pointer to the required data as they are
stored inside the hash table. The caller uses overloaded functions to
get the key and "mapped" values from this pointer. Such an interface
avoids the need for constructing iterator-like wrapper objects, which is
especially important for compound hash tables such as the future
StringHashMap.
2019-09-24 17:44:35 +03:00

558 lines
20 KiB
C++

#pragma once
#include <Common/HashTable/HashTable.h>
#include <Common/HashTable/HashTableKeyHolder.h>
#include <Common/ColumnsHashingImpl.h>
#include <Common/Arena.h>
#include <Common/LRUCache.h>
#include <Common/assert_cast.h>
#include <common/unaligned.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnFixedString.h>
#include <Columns/ColumnLowCardinality.h>
#include <Core/Defines.h>
#include <memory>
namespace DB
{
namespace ColumnsHashing
{
/// For the case when there is one numeric key.
/// UInt8/16/32/64 for any type with corresponding bit width.
template <typename Value, typename Mapped, typename FieldType, bool use_cache = true>
struct HashMethodOneNumber
: public columns_hashing_impl::HashMethodBase<HashMethodOneNumber<Value, Mapped, FieldType, use_cache>, Value, Mapped, use_cache>
{
using Self = HashMethodOneNumber<Value, Mapped, FieldType, use_cache>;
using Base = columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
const char * vec;
/// If the keys of a fixed length then key_sizes contains their lengths, empty otherwise.
HashMethodOneNumber(const ColumnRawPtrs & key_columns, const Sizes & /*key_sizes*/, const HashMethodContextPtr &)
{
vec = key_columns[0]->getRawData().data;
}
HashMethodOneNumber(const IColumn * column)
{
vec = column->getRawData().data;
}
/// Creates context. Method is called once and result context is used in all threads.
using Base::createContext; /// (const HashMethodContext::Settings &) -> HashMethodContextPtr
/// Emplace key into HashTable or HashMap. If Data is HashMap, returns ptr to value, otherwise nullptr.
/// Data is a HashTable where to insert key from column's row.
/// For Serialized method, key may be placed in pool.
using Base::emplaceKey; /// (Data & data, size_t row, Arena & pool) -> EmplaceResult
/// Find key into HashTable or HashMap. If Data is HashMap and key was found, returns ptr to value, otherwise nullptr.
using Base::findKey; /// (Data & data, size_t row, Arena & pool) -> FindResult
/// Get hash value of row.
using Base::getHash; /// (const Data & data, size_t row, Arena & pool) -> size_t
/// Is used for default implementation in HashMethodBase.
FieldType getKeyHolder(size_t row, Arena &) const { return unalignedLoad<FieldType>(vec + row * sizeof(FieldType)); }
};
/// For the case when there is one string key.
template <typename Value, typename Mapped, bool place_string_to_arena = true, bool use_cache = true>
struct HashMethodString
: public columns_hashing_impl::HashMethodBase<HashMethodString<Value, Mapped, place_string_to_arena, use_cache>, Value, Mapped, use_cache>
{
using Self = HashMethodString<Value, Mapped, place_string_to_arena, use_cache>;
using Base = columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
const IColumn::Offset * offsets;
const UInt8 * chars;
HashMethodString(const ColumnRawPtrs & key_columns, const Sizes & /*key_sizes*/, const HashMethodContextPtr &)
{
const IColumn & column = *key_columns[0];
const ColumnString & column_string = assert_cast<const ColumnString &>(column);
offsets = column_string.getOffsets().data();
chars = column_string.getChars().data();
}
auto getKeyHolder(ssize_t row, [[maybe_unused]] Arena & pool) const
{
StringRef key(chars + offsets[row - 1], offsets[row] - offsets[row - 1] - 1);
if constexpr (place_string_to_arena)
{
return ArenaKeyHolder{key, pool};
}
else
{
return key;
}
}
protected:
friend class columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
};
/// For the case when there is one fixed-length string key.
template <typename Value, typename Mapped, bool place_string_to_arena = true, bool use_cache = true>
struct HashMethodFixedString
: public columns_hashing_impl::HashMethodBase<HashMethodFixedString<Value, Mapped, place_string_to_arena, use_cache>, Value, Mapped, use_cache>
{
using Self = HashMethodFixedString<Value, Mapped, place_string_to_arena, use_cache>;
using Base = columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
size_t n;
const ColumnFixedString::Chars * chars;
HashMethodFixedString(const ColumnRawPtrs & key_columns, const Sizes & /*key_sizes*/, const HashMethodContextPtr &)
{
const IColumn & column = *key_columns[0];
const ColumnFixedString & column_string = assert_cast<const ColumnFixedString &>(column);
n = column_string.getN();
chars = &column_string.getChars();
}
auto getKeyHolder(size_t row, [[maybe_unused]] Arena & pool) const
{
StringRef key(&(*chars)[row * n], n);
if constexpr (place_string_to_arena)
{
return ArenaKeyHolder{key, pool};
}
else
{
return key;
}
}
protected:
friend class columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
};
/// Cache stores dictionaries and saved_hash per dictionary key.
class LowCardinalityDictionaryCache : public HashMethodContext
{
public:
/// Will assume that dictionaries with same hash has the same keys.
/// Just in case, check that they have also the same size.
struct DictionaryKey
{
UInt128 hash;
UInt64 size;
bool operator== (const DictionaryKey & other) const { return hash == other.hash && size == other.size; }
};
struct DictionaryKeyHash
{
size_t operator()(const DictionaryKey & key) const
{
SipHash hash;
hash.update(key.hash.low);
hash.update(key.hash.high);
hash.update(key.size);
return hash.get64();
}
};
struct CachedValues
{
/// Store ptr to dictionary to be sure it won't be deleted.
ColumnPtr dictionary_holder;
/// Hashes for dictionary keys.
const UInt64 * saved_hash = nullptr;
};
using CachedValuesPtr = std::shared_ptr<CachedValues>;
explicit LowCardinalityDictionaryCache(const HashMethodContext::Settings & settings) : cache(settings.max_threads) {}
CachedValuesPtr get(const DictionaryKey & key) { return cache.get(key); }
void set(const DictionaryKey & key, const CachedValuesPtr & mapped) { cache.set(key, mapped); }
private:
using Cache = LRUCache<DictionaryKey, CachedValues, DictionaryKeyHash>;
Cache cache;
};
/// Single low cardinality column.
template <typename SingleColumnMethod, typename Mapped, bool use_cache>
struct HashMethodSingleLowCardinalityColumn : public SingleColumnMethod
{
using Base = SingleColumnMethod;
enum class VisitValue
{
Empty = 0,
Found = 1,
NotFound = 2,
};
static constexpr bool has_mapped = !std::is_same<Mapped, void>::value;
using EmplaceResult = columns_hashing_impl::EmplaceResultImpl<Mapped>;
using FindResult = columns_hashing_impl::FindResultImpl<Mapped>;
static HashMethodContextPtr createContext(const HashMethodContext::Settings & settings)
{
return std::make_shared<LowCardinalityDictionaryCache>(settings);
}
ColumnRawPtrs key_columns;
const IColumn * positions = nullptr;
size_t size_of_index_type = 0;
/// saved hash is from current column or from cache.
const UInt64 * saved_hash = nullptr;
/// Hold dictionary in case saved_hash is from cache to be sure it won't be deleted.
ColumnPtr dictionary_holder;
/// Cache AggregateDataPtr for current column in order to decrease the number of hash table usages.
columns_hashing_impl::MappedCache<Mapped> mapped_cache;
PaddedPODArray<VisitValue> visit_cache;
/// If initialized column is nullable.
bool is_nullable = false;
static const ColumnLowCardinality & getLowCardinalityColumn(const IColumn * low_cardinality_column)
{
auto column = typeid_cast<const ColumnLowCardinality *>(low_cardinality_column);
if (!column)
throw Exception("Invalid aggregation key type for HashMethodSingleLowCardinalityColumn method. "
"Excepted LowCardinality, got " + column->getName(), ErrorCodes::LOGICAL_ERROR);
return *column;
}
HashMethodSingleLowCardinalityColumn(
const ColumnRawPtrs & key_columns_low_cardinality, const Sizes & key_sizes, const HashMethodContextPtr & context)
: Base({getLowCardinalityColumn(key_columns_low_cardinality[0]).getDictionary().getNestedNotNullableColumn().get()}, key_sizes, context)
{
auto column = &getLowCardinalityColumn(key_columns_low_cardinality[0]);
if (!context)
throw Exception("Cache wasn't created for HashMethodSingleLowCardinalityColumn",
ErrorCodes::LOGICAL_ERROR);
LowCardinalityDictionaryCache * lcd_cache;
if constexpr (use_cache)
{
lcd_cache = typeid_cast<LowCardinalityDictionaryCache *>(context.get());
if (!lcd_cache)
{
const auto & cached_val = *context;
throw Exception("Invalid type for HashMethodSingleLowCardinalityColumn cache: "
+ demangle(typeid(cached_val).name()), ErrorCodes::LOGICAL_ERROR);
}
}
auto * dict = column->getDictionary().getNestedNotNullableColumn().get();
is_nullable = column->getDictionary().nestedColumnIsNullable();
key_columns = {dict};
bool is_shared_dict = column->isSharedDictionary();
typename LowCardinalityDictionaryCache::DictionaryKey dictionary_key;
typename LowCardinalityDictionaryCache::CachedValuesPtr cached_values;
if (is_shared_dict)
{
dictionary_key = {column->getDictionary().getHash(), dict->size()};
if constexpr (use_cache)
cached_values = lcd_cache->get(dictionary_key);
}
if (cached_values)
{
saved_hash = cached_values->saved_hash;
dictionary_holder = cached_values->dictionary_holder;
}
else
{
saved_hash = column->getDictionary().tryGetSavedHash();
dictionary_holder = column->getDictionaryPtr();
if constexpr (use_cache)
{
if (is_shared_dict)
{
cached_values = std::make_shared<typename LowCardinalityDictionaryCache::CachedValues>();
cached_values->saved_hash = saved_hash;
cached_values->dictionary_holder = dictionary_holder;
lcd_cache->set(dictionary_key, cached_values);
}
}
}
if constexpr (has_mapped)
mapped_cache.resize(key_columns[0]->size());
VisitValue empty(VisitValue::Empty);
visit_cache.assign(key_columns[0]->size(), empty);
size_of_index_type = column->getSizeOfIndexType();
positions = column->getIndexesPtr().get();
}
ALWAYS_INLINE size_t getIndexAt(size_t row) const
{
switch (size_of_index_type)
{
case sizeof(UInt8): return assert_cast<const ColumnUInt8 *>(positions)->getElement(row);
case sizeof(UInt16): return assert_cast<const ColumnUInt16 *>(positions)->getElement(row);
case sizeof(UInt32): return assert_cast<const ColumnUInt32 *>(positions)->getElement(row);
case sizeof(UInt64): return assert_cast<const ColumnUInt64 *>(positions)->getElement(row);
default: throw Exception("Unexpected size of index type for low cardinality column.", ErrorCodes::LOGICAL_ERROR);
}
}
/// Get the key holder from the key columns for insertion into the hash table.
ALWAYS_INLINE auto getKeyHolder(size_t row, Arena & pool) const
{
return Base::getKeyHolder(getIndexAt(row), pool);
}
template <typename Data>
ALWAYS_INLINE EmplaceResult emplaceKey(Data & data, size_t row_, Arena & pool)
{
size_t row = getIndexAt(row_);
if (is_nullable && row == 0)
{
visit_cache[row] = VisitValue::Found;
bool has_null_key = data.hasNullKeyData();
data.hasNullKeyData() = true;
if constexpr (has_mapped)
return EmplaceResult(data.getNullKeyData(), mapped_cache[0], !has_null_key);
else
return EmplaceResult(!has_null_key);
}
if (visit_cache[row] == VisitValue::Found)
{
if constexpr (has_mapped)
return EmplaceResult(mapped_cache[row], mapped_cache[row], false);
else
return EmplaceResult(false);
}
auto key_holder = getKeyHolder(row_, pool);
bool inserted = false;
typename Data::LookupResult it;
if (saved_hash)
data.emplace(key_holder, it, inserted, saved_hash[row]);
else
data.emplace(key_holder, it, inserted);
visit_cache[row] = VisitValue::Found;
if constexpr (has_mapped)
{
auto & mapped = *lookupResultGetMapped(it);
if (inserted)
{
new (&mapped) Mapped();
}
mapped_cache[row] = mapped;
return EmplaceResult(mapped, mapped_cache[row], inserted);
}
else
return EmplaceResult(inserted);
}
ALWAYS_INLINE bool isNullAt(size_t i)
{
if (!is_nullable)
return false;
return getIndexAt(i) == 0;
}
template <typename Data>
ALWAYS_INLINE FindResult findFromRow(Data & data, size_t row_, Arena & pool)
{
size_t row = getIndexAt(row_);
if (is_nullable && row == 0)
{
if constexpr (has_mapped)
return FindResult(data.hasNullKeyData() ? &data.getNullKeyData() : nullptr, data.hasNullKeyData());
else
return FindResult(data.hasNullKeyData());
}
if (visit_cache[row] != VisitValue::Empty)
{
if constexpr (has_mapped)
return FindResult(&mapped_cache[row], visit_cache[row] == VisitValue::Found);
else
return FindResult(visit_cache[row] == VisitValue::Found);
}
auto key_holder = getKeyHolder(row_, pool);
typename Data::iterator it;
if (saved_hash)
it = data.find(*key_holder, saved_hash[row]);
else
it = data.find(*key_holder);
bool found = it != data.end();
visit_cache[row] = found ? VisitValue::Found : VisitValue::NotFound;
if constexpr (has_mapped)
{
if (found)
mapped_cache[row] = it->second;
}
if constexpr (has_mapped)
return FindResult(&mapped_cache[row], found);
else
return FindResult(found);
}
template <typename Data>
ALWAYS_INLINE size_t getHash(const Data & data, size_t row, Arena & pool)
{
row = getIndexAt(row);
if (saved_hash)
return saved_hash[row];
return Base::getHash(data, row, pool);
}
};
// Optional mask for low cardinality columns.
template <bool has_low_cardinality>
struct LowCardinalityKeys
{
ColumnRawPtrs nested_columns;
ColumnRawPtrs positions;
Sizes position_sizes;
};
template <>
struct LowCardinalityKeys<false> {};
/// For the case when all keys are of fixed length, and they fit in N (for example, 128) bits.
template <typename Value, typename Key, typename Mapped, bool has_nullable_keys_ = false, bool has_low_cardinality_ = false, bool use_cache = true>
struct HashMethodKeysFixed
: private columns_hashing_impl::BaseStateKeysFixed<Key, has_nullable_keys_>
, public columns_hashing_impl::HashMethodBase<HashMethodKeysFixed<Value, Key, Mapped, has_nullable_keys_, has_low_cardinality_, use_cache>, Value, Mapped, use_cache>
{
using Self = HashMethodKeysFixed<Value, Key, Mapped, has_nullable_keys_, has_low_cardinality_, use_cache>;
using BaseHashed = columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
using Base = columns_hashing_impl::BaseStateKeysFixed<Key, has_nullable_keys_>;
static constexpr bool has_nullable_keys = has_nullable_keys_;
static constexpr bool has_low_cardinality = has_low_cardinality_;
LowCardinalityKeys<has_low_cardinality> low_cardinality_keys;
Sizes key_sizes;
size_t keys_size;
HashMethodKeysFixed(const ColumnRawPtrs & key_columns, const Sizes & key_sizes_, const HashMethodContextPtr &)
: Base(key_columns), key_sizes(std::move(key_sizes_)), keys_size(key_columns.size())
{
if constexpr (has_low_cardinality)
{
low_cardinality_keys.nested_columns.resize(key_columns.size());
low_cardinality_keys.positions.assign(key_columns.size(), nullptr);
low_cardinality_keys.position_sizes.resize(key_columns.size());
for (size_t i = 0; i < key_columns.size(); ++i)
{
if (auto * low_cardinality_col = typeid_cast<const ColumnLowCardinality *>(key_columns[i]))
{
low_cardinality_keys.nested_columns[i] = low_cardinality_col->getDictionary().getNestedColumn().get();
low_cardinality_keys.positions[i] = &low_cardinality_col->getIndexes();
low_cardinality_keys.position_sizes[i] = low_cardinality_col->getSizeOfIndexType();
}
else
low_cardinality_keys.nested_columns[i] = key_columns[i];
}
}
}
ALWAYS_INLINE Key getKeyHolder(size_t row, Arena &) const
{
if constexpr (has_nullable_keys)
{
auto bitmap = Base::createBitmap(row);
return packFixed<Key>(row, keys_size, Base::getActualColumns(), key_sizes, bitmap);
}
else
{
if constexpr (has_low_cardinality)
return packFixed<Key, true>(row, keys_size, low_cardinality_keys.nested_columns, key_sizes,
&low_cardinality_keys.positions, &low_cardinality_keys.position_sizes);
return packFixed<Key>(row, keys_size, Base::getActualColumns(), key_sizes);
}
}
};
/** Hash by concatenating serialized key values.
* The serialized value differs in that it uniquely allows to deserialize it, having only the position with which it starts.
* That is, for example, for strings, it contains first the serialized length of the string, and then the bytes.
* Therefore, when aggregating by several strings, there is no ambiguity.
*/
template <typename Value, typename Mapped>
struct HashMethodSerialized
: public columns_hashing_impl::HashMethodBase<HashMethodSerialized<Value, Mapped>, Value, Mapped, false>
{
using Self = HashMethodSerialized<Value, Mapped>;
using Base = columns_hashing_impl::HashMethodBase<Self, Value, Mapped, false>;
ColumnRawPtrs key_columns;
size_t keys_size;
HashMethodSerialized(const ColumnRawPtrs & key_columns_, const Sizes & /*key_sizes*/, const HashMethodContextPtr &)
: key_columns(key_columns_), keys_size(key_columns_.size()) {}
protected:
friend class columns_hashing_impl::HashMethodBase<Self, Value, Mapped, false>;
ALWAYS_INLINE SerializedKeyHolder getKeyHolder(size_t row, Arena & pool) const
{
return SerializedKeyHolder{
serializeKeysToPoolContiguous(row, keys_size, key_columns, pool),
pool};
}
};
/// For the case when there is one string key.
template <typename Value, typename Mapped, bool use_cache = true>
struct HashMethodHashed
: public columns_hashing_impl::HashMethodBase<HashMethodHashed<Value, Mapped, use_cache>, Value, Mapped, use_cache>
{
using Key = UInt128;
using Self = HashMethodHashed<Value, Mapped, use_cache>;
using Base = columns_hashing_impl::HashMethodBase<Self, Value, Mapped, use_cache>;
ColumnRawPtrs key_columns;
HashMethodHashed(ColumnRawPtrs key_columns_, const Sizes &, const HashMethodContextPtr &)
: key_columns(std::move(key_columns_)) {}
ALWAYS_INLINE Key getKeyHolder(size_t row, Arena &) const
{
return hash128(row, key_columns.size(), key_columns);
}
};
}
}