ClickHouse/dbms/src/Interpreters/SetVariants.h

#pragma once

#include <Columns/ColumnNullable.h>
#include <Columns/ColumnString.h>
#include <Interpreters/AggregationCommon.h>
#include <Common/ColumnsHashing.h>
#include <Common/assert_cast.h>
#include <Common/Arena.h>
#include <Common/HashTable/HashSet.h>
#include <Common/HashTable/ClearableHashSet.h>
#include <Common/HashTable/FixedClearableHashSet.h>
#include <Common/HashTable/FixedHashSet.h>
#include <Common/UInt128.h>


namespace DB
{

/** Methods for different implementations of sets (used in right hand side of IN or for DISTINCT).
  * To use as template parameter.
  */


/// For the case where there is one numeric key.
template <typename FieldType, typename TData>    /// UInt8/16/32/64 for any types with corresponding bit width.
struct SetMethodOneNumber
{
    using Data = TData;
    using Key = typename Data::key_type;

    Data data;

    using State = ColumnsHashing::HashMethodOneNumber<typename Data::value_type, void, FieldType>;
};

/// For the case where there is one string key.
template <typename TData>
struct SetMethodString
{
    using Data = TData;
    using Key = typename Data::key_type;

    Data data;

    using State = ColumnsHashing::HashMethodString<typename Data::value_type, void, true, false>;
};

/// For the case when there is one fixed-length string key.
template <typename TData>
struct SetMethodFixedString
{
    using Data = TData;
    using Key = typename Data::key_type;

    Data data;

    using State = ColumnsHashing::HashMethodFixedString<typename Data::value_type, void, true, false>;
};

namespace set_impl
{

/// This class is designed to provide the functionality that is required for
/// supporting nullable keys in SetMethodKeysFixed. If there are
/// no nullable keys, this class is merely implemented as an empty shell.
template <typename Key, bool has_nullable_keys>
class BaseStateKeysFixed;

/// Case where nullable keys are supported.
template <typename Key>
class BaseStateKeysFixed<Key, true>
{
protected:
    void init(const ColumnRawPtrs & key_columns)
    {
        null_maps.reserve(key_columns.size());
        actual_columns.reserve(key_columns.size());

        for (const auto & col : key_columns)
        {
            if (auto * nullable = checkAndGetColumn<ColumnNullable>(*col))
            {
                actual_columns.push_back(&nullable->getNestedColumn());
                null_maps.push_back(&nullable->getNullMapColumn());
            }
            else
            {
                actual_columns.push_back(col);
                null_maps.push_back(nullptr);
            }
        }
    }

    /// Return the columns which actually contain the values of the keys.
    /// For a given key column, if it is nullable, we return its nested
    /// column. Otherwise we return the key column itself.
    inline const ColumnRawPtrs & getActualColumns() const
    {
        return actual_columns;
    }

    /// Create a bitmap that indicates whether, for a particular row,
    /// a key column bears a null value or not.
    KeysNullMap<Key> createBitmap(size_t row) const
    {
        KeysNullMap<Key> bitmap{};

        for (size_t k = 0; k < null_maps.size(); ++k)
        {
            if (null_maps[k] != nullptr)
            {
                const auto & null_map = assert_cast<const ColumnUInt8 &>(*null_maps[k]).getData();
                if (null_map[row] == 1)
                {
                    size_t bucket = k / 8;
                    size_t offset = k % 8;
                    bitmap[bucket] |= UInt8(1) << offset;
                }
            }
        }

        return bitmap;
    }

private:
    ColumnRawPtrs actual_columns;
    ColumnRawPtrs null_maps;
};

/// Case where nullable keys are not supported.
template <typename Key>
class BaseStateKeysFixed<Key, false>
{
protected:
    void init(const ColumnRawPtrs &)
    {
        throw Exception{"Internal error: calling init() for non-nullable"
            " keys is forbidden", ErrorCodes::LOGICAL_ERROR};
    }

    const ColumnRawPtrs & getActualColumns() const
    {
        throw Exception{"Internal error: calling getActualColumns() for non-nullable"
            " keys is forbidden", ErrorCodes::LOGICAL_ERROR};
    }

    KeysNullMap<Key> createBitmap(size_t) const
    {
        throw Exception{"Internal error: calling createBitmap() for non-nullable keys"
            " is forbidden", ErrorCodes::LOGICAL_ERROR};
    }
};

}

/// For the case when all keys are of fixed length, and they fit in N (for example, 128) bits.
template <typename TData, bool has_nullable_keys_ = false>
struct SetMethodKeysFixed
{
    using Data = TData;
    using Key = typename Data::key_type;
    static constexpr bool has_nullable_keys = has_nullable_keys_;

    Data data;

    using State = ColumnsHashing::HashMethodKeysFixed<typename Data::value_type, Key, void, has_nullable_keys, false>;
};

/// For other cases. 128 bit hash from the key.
template <typename TData>
struct SetMethodHashed
{
    using Data = TData;
    using Key = typename Data::key_type;

    Data data;

    using State = ColumnsHashing::HashMethodHashed<typename Data::value_type, void>;
};


/** Different implementations of the set.
  */
struct NonClearableSet
{
    std::unique_ptr<SetMethodOneNumber<UInt8, FixedHashSet<UInt8>>>                                             key8;
    std::unique_ptr<SetMethodOneNumber<UInt16, FixedHashSet<UInt16>>>                                           key16;

    /** Also for the experiment was tested the ability to use SmallSet,
      *  as long as the number of elements in the set is small (and, if necessary, converted to a full-fledged HashSet).
      * But this experiment showed that there is an advantage only in rare cases.
      */
    std::unique_ptr<SetMethodOneNumber<UInt32, HashSet<UInt32, HashCRC32<UInt32>>>>                             key32;
    std::unique_ptr<SetMethodOneNumber<UInt64, HashSet<UInt64, HashCRC32<UInt64>>>>                             key64;
    std::unique_ptr<SetMethodString<HashSetWithSavedHash<StringRef>>>                                           key_string;
    std::unique_ptr<SetMethodFixedString<HashSetWithSavedHash<StringRef>>>                                      key_fixed_string;
    std::unique_ptr<SetMethodKeysFixed<HashSet<UInt128, UInt128HashCRC32>>>                                     keys128;
    std::unique_ptr<SetMethodKeysFixed<HashSet<UInt256, UInt256HashCRC32>>>                                     keys256;
    std::unique_ptr<SetMethodHashed<HashSet<UInt128, UInt128TrivialHash>>>                                      hashed;

    /// Support for nullable keys (for DISTINCT implementation).
    std::unique_ptr<SetMethodKeysFixed<HashSet<UInt128, UInt128HashCRC32>, true>>                               nullable_keys128;
    std::unique_ptr<SetMethodKeysFixed<HashSet<UInt256, UInt256HashCRC32>, true>>                               nullable_keys256;
    /** Unlike Aggregator, `concat` method is not used here.
      * This is done because `hashed` method, although slower, but in this case, uses less RAM.
      *  since when you use it, the key values themselves are not stored.
      */
};

struct ClearableSet
{
    std::unique_ptr<SetMethodOneNumber<UInt8, FixedClearableHashSet<UInt8>>>                                        key8;
    std::unique_ptr<SetMethodOneNumber<UInt16, FixedClearableHashSet<UInt16>>>                                      key16;

    std::unique_ptr<SetMethodOneNumber<UInt32, ClearableHashSet<UInt32, HashCRC32<UInt32>>>>                        key32;
    std::unique_ptr<SetMethodOneNumber<UInt64, ClearableHashSet<UInt64, HashCRC32<UInt64>>>>                        key64;
    std::unique_ptr<SetMethodString<ClearableHashSetWithSavedHash<StringRef>>>                                      key_string;
    std::unique_ptr<SetMethodFixedString<ClearableHashSetWithSavedHash<StringRef>>>                                 key_fixed_string;
    std::unique_ptr<SetMethodKeysFixed<ClearableHashSet<UInt128, UInt128HashCRC32>>>                                keys128;
    std::unique_ptr<SetMethodKeysFixed<ClearableHashSet<UInt256, UInt256HashCRC32>>>                                keys256;
    std::unique_ptr<SetMethodHashed<ClearableHashSet<UInt128, UInt128TrivialHash>>>                                 hashed;

    /// Support for nullable keys (for DISTINCT implementation).
    std::unique_ptr<SetMethodKeysFixed<ClearableHashSet<UInt128, UInt128HashCRC32>, true>>                          nullable_keys128;
    std::unique_ptr<SetMethodKeysFixed<ClearableHashSet<UInt256, UInt256HashCRC32>, true>>                          nullable_keys256;
    /** Unlike Aggregator, `concat` method is not used here.
      * This is done because `hashed` method, although slower, but in this case, uses less RAM.
      *  since when you use it, the key values themselves are not stored.
      */
};

template <typename Variant>
struct SetVariantsTemplate: public Variant
{
    Arena string_pool;

    #define APPLY_FOR_SET_VARIANTS(M) \
        M(key8)                 \
        M(key16)                \
        M(key32)                \
        M(key64)                \
        M(key_string)           \
        M(key_fixed_string)     \
        M(keys128)              \
        M(keys256)              \
        M(nullable_keys128)     \
        M(nullable_keys256)     \
        M(hashed)

    #define M(NAME) using Variant::NAME;
        APPLY_FOR_SET_VARIANTS(M)
    #undef M

    enum class Type
    {
        EMPTY,

    #define M(NAME) NAME,
        APPLY_FOR_SET_VARIANTS(M)
    #undef M
    };

    Type type = Type::EMPTY;

    bool empty() const { return type == Type::EMPTY; }

    static Type chooseMethod(const ColumnRawPtrs & key_columns, Sizes & key_sizes);

    void init(Type type_);

    size_t getTotalRowCount() const;
    /// Counts the size in bytes of the Set buffer and the size of the `string_pool`
    size_t getTotalByteCount() const;
};

using SetVariants = SetVariantsTemplate<NonClearableSet>;
using ClearableSetVariants = SetVariantsTemplate<ClearableSet>;

}