be/src/exprs/aggregate/aggregate_function_approx_count_distinct.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#pragma once

#include <stddef.h>
#include <stdint.h>

#include <memory>
#include <string>

#include "core/assert_cast.h"
#include "core/column/column_decimal.h"
#include "core/data_type/data_type_number.h"
#include "core/string_ref.h"
#include "core/types.h"
#include "core/value/hll.h"
#include "exprs/aggregate/aggregate_function.h"
#include "exprs/aggregate/aggregate_function_simple_factory.h"
#include "util/hash_util.hpp"
#include "util/slice.h"

namespace doris {
#include "common/compile_check_begin.h"
class Arena;
class BufferReadable;
class BufferWritable;
class IColumn;
} // namespace doris

namespace doris {

struct AggregateFunctionApproxCountDistinctData {
    HyperLogLog hll_data;

    void add(uint64_t hash_value) {
        if (hash_value != 0) {
            hll_data.update(hash_value);
        }
    }

    void merge(const AggregateFunctionApproxCountDistinctData& rhs) {
        hll_data.merge(rhs.hll_data);
    }

    void write(BufferWritable& buf) const {
        std::string result;
        result.resize(hll_data.max_serialized_size());
        result.resize(hll_data.serialize((uint8_t*)result.data()));
        buf.write_binary(result);
    }

    void read(BufferReadable& buf) {
        StringRef result;
        buf.read_binary(result);
        Slice data = Slice(result.data, result.size);
        hll_data.deserialize(data);
    }

    int64_t get() const { return hll_data.estimate_cardinality(); }

    void reset() { hll_data.clear(); }
};

template <PrimitiveType type>
class AggregateFunctionApproxCountDistinct final
        : public IAggregateFunctionDataHelper<AggregateFunctionApproxCountDistinctData,
                                              AggregateFunctionApproxCountDistinct<type>>,
          UnaryExpression,
          NotNullableAggregateFunction {
public:
    using ColumnDataType = typename PrimitiveTypeTraits<type>::ColumnType;
    String get_name() const override { return "approx_count_distinct"; }

    AggregateFunctionApproxCountDistinct(const DataTypes& argument_types_)
            : IAggregateFunctionDataHelper<AggregateFunctionApproxCountDistinctData,
                                           AggregateFunctionApproxCountDistinct<type>>(
                      argument_types_) {}

    DataTypePtr get_return_type() const override { return std::make_shared<DataTypeInt64>(); }

    void add(AggregateDataPtr __restrict place, const IColumn** columns, ssize_t row_num,
             Arena&) const override {
        if constexpr (is_decimal(type) || is_int_or_bool(type) || is_ip(type) ||
                      is_date_type(type) || is_timestamptz_type(type) || is_float_or_double(type) ||
                      type == TYPE_TIME || type == TYPE_TIMEV2) {
            auto column =
                    assert_cast<const ColumnDataType*, TypeCheckOnRelease::DISABLE>(columns[0]);
            auto value = column->get_element(row_num);
            this->data(place).add(
                    HashUtil::murmur_hash64A((char*)&value, sizeof(value), HashUtil::MURMUR_SEED));
        } else {
            auto value = assert_cast<const ColumnDataType*, TypeCheckOnRelease::DISABLE>(columns[0])
                                 ->get_data_at(row_num);
            uint64_t hash_value =
                    HashUtil::murmur_hash64A(value.data, value.size, HashUtil::MURMUR_SEED);
            this->data(place).add(hash_value);
        }
    }

    void reset(AggregateDataPtr place) const override { this->data(place).reset(); }

    void merge(AggregateDataPtr __restrict place, ConstAggregateDataPtr rhs,
               Arena&) const override {
        this->data(place).merge(this->data(rhs));
    }

    void serialize(ConstAggregateDataPtr __restrict place, BufferWritable& buf) const override {
        this->data(place).write(buf);
    }

    void deserialize(AggregateDataPtr __restrict place, BufferReadable& buf,
                     Arena&) const override {
        this->data(place).read(buf);
    }

    void insert_result_into(ConstAggregateDataPtr __restrict place, IColumn& to) const override {
        auto& column = assert_cast<ColumnInt64&>(to);
        column.get_data().push_back(this->data(place).get());
    }
};

} // namespace doris

#include "common/compile_check_end.h"