ClickHouse/dbms/src/Interpreters/SetVariants.cpp

#include <Columns/ColumnString.h>
#include <Columns/ColumnConst.h>
#include <Common/typeid_cast.h>
#include <Common/assert_cast.h>
#include <Interpreters/SetVariants.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
}

template <typename Variant>
void SetVariantsTemplate<Variant>::init(Type type_)
{
    type = type_;

    switch (type)
    {
        case Type::EMPTY: break;

    #define M(NAME) \
        case Type::NAME: NAME = std::make_unique<typename decltype(NAME)::element_type>(); break;
        APPLY_FOR_SET_VARIANTS(M)
    #undef M
    }
}

template <typename Variant>
size_t SetVariantsTemplate<Variant>::getTotalRowCount() const
{
    switch (type)
    {
        case Type::EMPTY: return 0;

    #define M(NAME) \
        case Type::NAME: return NAME->data.size();
        APPLY_FOR_SET_VARIANTS(M)
    #undef M
    }

    __builtin_unreachable();
}

template <typename Variant>
size_t SetVariantsTemplate<Variant>::getTotalByteCount() const
{
    switch (type)
    {
        case Type::EMPTY: return 0;

    #define M(NAME) \
        case Type::NAME: return NAME->data.getBufferSizeInBytes();
        APPLY_FOR_SET_VARIANTS(M)
    #undef M
    }

    __builtin_unreachable();
}

template <typename Variant>
typename SetVariantsTemplate<Variant>::Type SetVariantsTemplate<Variant>::chooseMethod(const ColumnRawPtrs & key_columns, Sizes & key_sizes)
{
    /// Check if at least one of the specified keys is nullable.
    /// Create a set of nested key columns from the corresponding key columns.
    /// Here "nested" means that, if a key column is nullable, we take its nested
    /// column; otherwise we take the key column as is.
    ColumnRawPtrs nested_key_columns;
    nested_key_columns.reserve(key_columns.size());
    bool has_nullable_key = false;

    for (const auto & col : key_columns)
    {
        if (auto * nullable = checkAndGetColumn<ColumnNullable>(*col))
        {
            nested_key_columns.push_back(&nullable->getNestedColumn());
            has_nullable_key = true;
        }
        else
            nested_key_columns.push_back(col);
    }

    size_t keys_size = nested_key_columns.size();

    bool all_fixed = true;
    size_t keys_bytes = 0;
    key_sizes.resize(keys_size);
    for (size_t j = 0; j < keys_size; ++j)
    {
        if (!nested_key_columns[j]->isFixedAndContiguous())
        {
            all_fixed = false;
            break;
        }
        key_sizes[j] = nested_key_columns[j]->sizeOfValueIfFixed();
        keys_bytes += key_sizes[j];
    }

    if (has_nullable_key)
    {
        /// At least one key is nullable. Therefore we choose a method
        /// that takes into account this fact.
        if ((keys_size == 1) && (nested_key_columns[0]->isNumeric()))
        {
            /// We have exactly one key and it is nullable. We shall add it a tag
            /// which specifies whether its value is null or not.
            size_t size_of_field = nested_key_columns[0]->sizeOfValueIfFixed();
            if ((size_of_field == 1) || (size_of_field == 2) || (size_of_field == 4) || (size_of_field == 8))
                return Type::nullable_keys128;
            else
                throw Exception{"Logical error: numeric column has sizeOfField not in 1, 2, 4, 8.",
                    ErrorCodes::LOGICAL_ERROR};
        }

        if (all_fixed)
        {
            /// Pack if possible all the keys along with information about which key values are nulls
            /// into a fixed 16- or 32-byte blob.
            if (keys_bytes > (std::numeric_limits<size_t>::max() - std::tuple_size<KeysNullMap<UInt128>>::value))
                throw Exception{"Aggregator: keys sizes overflow", ErrorCodes::LOGICAL_ERROR};
            if ((std::tuple_size<KeysNullMap<UInt128>>::value + keys_bytes) <= 16)
                return Type::nullable_keys128;
            if ((std::tuple_size<KeysNullMap<UInt256>>::value + keys_bytes) <= 32)
                return Type::nullable_keys256;
        }

        /// Fallback case.
        return Type::hashed;
    }

    /// If there is one numeric key that fits into 64 bits
    if (keys_size == 1 && nested_key_columns[0]->isNumeric() && !nested_key_columns[0]->lowCardinality())
    {
        size_t size_of_field = nested_key_columns[0]->sizeOfValueIfFixed();
        if (size_of_field == 1)
            return Type::key8;
        if (size_of_field == 2)
            return Type::key16;
        if (size_of_field == 4)
            return Type::key32;
        if (size_of_field == 8)
            return Type::key64;
        if (size_of_field == 16)
            return Type::keys128;
        throw Exception("Logical error: numeric column has sizeOfField not in 1, 2, 4, 8, 16.", ErrorCodes::LOGICAL_ERROR);
    }

    /// If the keys fit in N bits, we will use a hash table for N-bit-packed keys
    if (all_fixed && keys_bytes <= 16)
        return Type::keys128;
    if (all_fixed && keys_bytes <= 32)
        return Type::keys256;

    /// If there is single string key, use hash table of it's values.
    if (keys_size == 1
        && (typeid_cast<const ColumnString *>(nested_key_columns[0])
            || (isColumnConst(*nested_key_columns[0]) && typeid_cast<const ColumnString *>(&assert_cast<const ColumnConst *>(nested_key_columns[0])->getDataColumn()))))
        return Type::key_string;

    if (keys_size == 1 && typeid_cast<const ColumnFixedString *>(nested_key_columns[0]))
        return Type::key_fixed_string;

    /// Otherwise, will use set of cryptographic hashes of unambiguously serialized values.
    return Type::hashed;
}

template struct SetVariantsTemplate<NonClearableSet>;
template struct SetVariantsTemplate<ClearableSet>;

}