ClickHouse/dbms/include/DB/AggregateFunctions/AggregateFunctionUniqUpTo.h
alexey-milovidov 6d5bfc8c6f Refactoring of numeric DataTypes (#581)
* Better code [#CLICKHOUSE-2].

* Addition to prev. revision [#CLICKHOUSE-2].

* Addition to prev. revision [#CLICKHOUSE-2].

* Addition to prev. revision [#CLICKHOUSE-2].
2017-03-12 14:13:45 +04:00

262 lines
7.7 KiB
C++

#pragma once
#include <DB/Core/FieldVisitors.h>
#include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
#include <DB/AggregateFunctions/UniqVariadicHash.h>
#include <DB/DataTypes/DataTypesNumber.h>
#include <DB/DataTypes/DataTypeTuple.h>
#include <DB/Columns/ColumnsNumber.h>
namespace DB
{
/** Counts the number of unique values up to no more than specified in the parameter.
*
* Example: uniqUpTo(3)(UserID)
* - will count the number of unique visitors, return 1, 2, 3 or 4 if visitors > = 4.
*
* For strings, a non-cryptographic hash function is used, due to which the calculation may be a bit inaccurate.
*/
template <typename T>
struct __attribute__((__packed__)) AggregateFunctionUniqUpToData
{
/** If count == threshold + 1 - this means that it is "overflowed" (values greater than threshold).
* In this case (for example, after calling the merge function), the `data` array does not necessarily contain the initialized values
* - example: combine a state in which there are few values, with another state that has overflowed;
* then set count to `threshold + 1`, and values from another state are not copied.
*/
UInt8 count = 0;
T data[0];
size_t size() const
{
return count;
}
/// threshold - for how many elements there is room in a `data`.
void insert(T x, UInt8 threshold)
{
/// The state is already full - nothing needs to be done.
if (count > threshold)
return;
/// Linear search for the matching element.
for (size_t i = 0; i < count; ++i)
if (data[i] == x)
return;
/// Did not find the matching element. If there is room for one more element, insert it.
if (count < threshold)
data[count] = x;
/// After increasing count, the state may be overflowed.
++count;
}
void merge(const AggregateFunctionUniqUpToData<T> & rhs, UInt8 threshold)
{
if (count > threshold)
return;
if (rhs.count > threshold)
{
/// If `rhs` is overflowed, then set `count` too also overflowed for the current state.
count = rhs.count;
return;
}
for (size_t i = 0; i < rhs.count; ++i)
insert(rhs.data[i], threshold);
}
void write(WriteBuffer & wb, UInt8 threshold) const
{
writeBinary(count, wb);
/// Write values only if the state is not overflowed. Otherwise, they are not needed, and only the fact that the state is overflowed is important.
if (count <= threshold)
wb.write(reinterpret_cast<const char *>(&data[0]), count * sizeof(data[0]));
}
void read(ReadBuffer & rb, UInt8 threshold)
{
readBinary(count, rb);
if (count <= threshold)
rb.read(reinterpret_cast<char *>(&data[0]), count * sizeof(data[0]));
}
void addImpl(const IColumn & column, size_t row_num, UInt8 threshold)
{
insert(static_cast<const ColumnVector<T> &>(column).getData()[row_num], threshold);
}
};
/// For strings, their hashes are remembered.
template <>
struct AggregateFunctionUniqUpToData<String> : AggregateFunctionUniqUpToData<UInt64>
{
void addImpl(const IColumn & column, size_t row_num, UInt8 threshold)
{
/// Keep in mind that calculations are approximate.
StringRef value = column.getDataAt(row_num);
insert(CityHash64(value.data, value.size), threshold);
}
};
constexpr UInt8 uniq_upto_max_threshold = 100;
template <typename T>
class AggregateFunctionUniqUpTo final : public IUnaryAggregateFunction<AggregateFunctionUniqUpToData<T>, AggregateFunctionUniqUpTo<T> >
{
private:
UInt8 threshold = 5; /// Default value if the parameter is not specified.
public:
size_t sizeOfData() const override
{
return sizeof(AggregateFunctionUniqUpToData<T>) + sizeof(T) * threshold;
}
String getName() const override { return "uniqUpTo"; }
DataTypePtr getReturnType() const override
{
return std::make_shared<DataTypeUInt64>();
}
void setArgument(const DataTypePtr & argument)
{
}
void setParameters(const Array & params) override
{
if (params.size() != 1)
throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
UInt64 threshold_param = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), params[0]);
if (threshold_param > uniq_upto_max_threshold)
throw Exception("Too large parameter for aggregate function " + getName() + ". Maximum: " + toString(uniq_upto_max_threshold),
ErrorCodes::ARGUMENT_OUT_OF_BOUND);
threshold = threshold_param;
}
void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num, Arena *) const
{
this->data(place).addImpl(column, row_num, threshold);
}
void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena * arena) const override
{
this->data(place).merge(this->data(rhs), threshold);
}
void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
{
this->data(place).write(buf, threshold);
}
void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena *) const override
{
this->data(place).read(buf, threshold);
}
void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
{
static_cast<ColumnUInt64 &>(to).getData().push_back(this->data(place).size());
}
};
/** For multiple arguments. To compute, hashes them.
* You can pass multiple arguments as is; You can also pass one argument - a tuple.
* But (for the possibility of effective implementation), you can not pass several arguments, among which there are tuples.
*/
template <bool argument_is_tuple>
class AggregateFunctionUniqUpToVariadic final : public IAggregateFunctionHelper<AggregateFunctionUniqUpToData<UInt64>>
{
private:
size_t num_args = 0;
UInt8 threshold = 5; /// Default value if the parameter is not specified.
public:
size_t sizeOfData() const override
{
return sizeof(AggregateFunctionUniqUpToData<UInt64>) + sizeof(UInt64) * threshold;
}
String getName() const override { return "uniqUpTo"; }
DataTypePtr getReturnType() const override
{
return std::make_shared<DataTypeUInt64>();
}
void setArguments(const DataTypes & arguments) override
{
if (argument_is_tuple)
num_args = typeid_cast<const DataTypeTuple &>(*arguments[0]).getElements().size();
else
num_args = arguments.size();
}
void setParameters(const Array & params) override
{
if (params.size() != 1)
throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
UInt64 threshold_param = applyVisitor(FieldVisitorConvertToNumber<UInt64>(), params[0]);
if (threshold_param > uniq_upto_max_threshold)
throw Exception("Too large parameter for aggregate function " + getName() + ". Maximum: " + toString(uniq_upto_max_threshold),
ErrorCodes::ARGUMENT_OUT_OF_BOUND);
threshold = threshold_param;
}
void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *) const override
{
this->data(place).insert(UniqVariadicHash<false, argument_is_tuple>::apply(num_args, columns, row_num), threshold);
}
void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena * arena) const override
{
this->data(place).merge(this->data(rhs), threshold);
}
void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
{
this->data(place).write(buf, threshold);
}
void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena *) const override
{
this->data(place).read(buf, threshold);
}
void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
{
static_cast<ColumnUInt64 &>(to).getData().push_back(this->data(place).size());
}
static void addFree(const IAggregateFunction * that, AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *arena)
{
static_cast<const AggregateFunctionUniqUpToVariadic &>(*that).add(place, columns, row_num, arena);
}
IAggregateFunction::AddFunc getAddressOfAddFunction() const override final { return &addFree; }
};
}