ClickHouse/src/DataTypes/DataTypeLowCardinality.h

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#pragma once
#include <DataTypes/IDataType.h>
#include <Columns/IColumnUnique.h>
namespace DB
{
class DataTypeLowCardinality : public IDataType
{
private:
DataTypePtr dictionary_type;
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public:
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explicit DataTypeLowCardinality(DataTypePtr dictionary_type_);
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const DataTypePtr & getDictionaryType() const { return dictionary_type; }
String doGetName() const override
{
return "LowCardinality(" + dictionary_type->getName() + ")";
}
const char * getFamilyName() const override { return "LowCardinality"; }
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TypeIndex getTypeId() const override { return TypeIndex::LowCardinality; }
MutableColumnPtr createColumn() const override;
Field getDefault() const override;
bool equals(const IDataType & rhs) const override;
bool isParametric() const override { return true; }
bool haveSubtypes() const override { return true; }
bool cannotBeStoredInTables() const override { return dictionary_type->cannotBeStoredInTables(); }
bool shouldAlignRightInPrettyFormats() const override { return dictionary_type->shouldAlignRightInPrettyFormats(); }
bool textCanContainOnlyValidUTF8() const override { return dictionary_type->textCanContainOnlyValidUTF8(); }
bool isComparable() const override { return dictionary_type->isComparable(); }
bool canBeComparedWithCollation() const override { return dictionary_type->canBeComparedWithCollation(); }
bool canBeUsedAsVersion() const override { return dictionary_type->canBeUsedAsVersion(); }
bool isSummable() const override { return dictionary_type->isSummable(); }
bool canBeUsedInBitOperations() const override { return dictionary_type->canBeUsedInBitOperations(); }
bool canBeUsedInBooleanContext() const override { return dictionary_type->canBeUsedInBooleanContext(); }
bool isValueRepresentedByNumber() const override { return dictionary_type->isValueRepresentedByNumber(); }
bool isValueRepresentedByInteger() const override { return dictionary_type->isValueRepresentedByInteger(); }
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bool isValueRepresentedByUnsignedInteger() const override { return dictionary_type->isValueRepresentedByUnsignedInteger(); }
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bool isValueUnambiguouslyRepresentedInContiguousMemoryRegion() const override { return true; }
bool haveMaximumSizeOfValue() const override { return dictionary_type->haveMaximumSizeOfValue(); }
size_t getMaximumSizeOfValueInMemory() const override { return dictionary_type->getMaximumSizeOfValueInMemory(); }
size_t getSizeOfValueInMemory() const override { return dictionary_type->getSizeOfValueInMemory(); }
bool isCategorial() const override { return false; }
bool isNullable() const override { return false; }
bool onlyNull() const override { return false; }
bool lowCardinality() const override { return true; }
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bool supportsSparseSerialization() const override { return false; }
bool isLowCardinalityNullable() const override { return dictionary_type->isNullable(); }
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static MutableColumnUniquePtr createColumnUnique(const IDataType & keys_type);
static MutableColumnUniquePtr createColumnUnique(const IDataType & keys_type, MutableColumnPtr && keys);
private:
SerializationPtr doGetDefaultSerialization() const override;
template <typename ... Params>
using SerializeFunctionPtr = void (IDataType::*)(const IColumn &, size_t, Params ...) const;
template <typename... Params, typename... Args>
void serializeImpl(const IColumn & column, size_t row_num, SerializeFunctionPtr<Params...> func, Args &&... args) const;
template <typename ... Params>
using DeserializeFunctionPtr = void (IDataType::*)(IColumn &, Params ...) const;
template <typename ... Params, typename... Args>
void deserializeImpl(IColumn & column, DeserializeFunctionPtr<Params...> func, Args &&... args) const;
template <typename Creator>
static MutableColumnUniquePtr createColumnUniqueImpl(const IDataType & keys_type, const Creator & creator);
};
/// Returns dictionary type if type is DataTypeLowCardinality, type otherwise.
DataTypePtr removeLowCardinality(const DataTypePtr & type);
/// Remove LowCardinality recursively from all nested types.
DataTypePtr recursiveRemoveLowCardinality(const DataTypePtr & type);
/// Remove LowCardinality recursively from all nested columns.
ColumnPtr recursiveRemoveLowCardinality(const ColumnPtr & column);
/// Convert column of type from_type to type to_type by converting nested LowCardinality columns.
ColumnPtr recursiveLowCardinalityTypeConversion(const ColumnPtr & column, const DataTypePtr & from_type, const DataTypePtr & to_type);
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/// Removes LowCardinality and Nullable in a correct order and returns T
/// if the type is LowCardinality(T) or LowCardinality(Nullable(T)); type otherwise
DataTypePtr removeLowCardinalityAndNullable(const DataTypePtr & type);
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}