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72 lines
2.6 KiB
C++
72 lines
2.6 KiB
C++
#pragma once
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#include <DataTypes/IDataType.h>
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#include <Columns/ColumnVariant.h>
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#include <optional>
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namespace DB
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{
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/** Variant data type.
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* This type represents a union of other data types.
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* For example, type Variant(T1, T2, ..., TN) means that each row of this type
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* has a value of either type T1 or T2 or ... or TN or none of them (NULL value).
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* Nullable(...), LowCardinality(Nullable(...)) and Variant(...) types are not allowed
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* inside Variant type.
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* The order of nested types doesn't matter: Variant(T1, T2) = Variant(T2, T1).
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* To have global order of nested types we sort variants by type names on Variant creation.
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* The index of a variant in a sorted list is called global variant discriminator.
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*/
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class DataTypeVariant final : public IDataType
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{
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private:
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DataTypes variants;
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public:
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static constexpr bool is_parametric = true;
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explicit DataTypeVariant(const DataTypes & variants_);
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TypeIndex getTypeId() const override { return TypeIndex::Variant; }
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const char * getFamilyName() const override { return "Variant"; }
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bool canBeInsideNullable() const override { return false; }
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bool supportsSparseSerialization() const override { return false; }
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bool canBeInsideSparseColumns() const override { return false; }
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MutableColumnPtr createColumn() const override;
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Field getDefault() const override;
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bool equals(const IDataType & rhs) const override;
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bool isParametric() const override { return true; }
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bool isComparable() const override { return true; }
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bool haveSubtypes() const override { return true; }
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bool textCanContainOnlyValidUTF8() const override;
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bool haveMaximumSizeOfValue() const override;
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bool hasDynamicSubcolumnsDeprecated() const override;
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size_t getMaximumSizeOfValueInMemory() const override;
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const DataTypePtr & getVariant(size_t i) const { return variants[i]; }
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const DataTypes & getVariants() const { return variants; }
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/// Check if Variant has provided type in the list of variants and return its discriminator.
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std::optional<ColumnVariant::Discriminator> tryGetVariantDiscriminator(const String & type_name) const;
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void forEachChild(const ChildCallback & callback) const override;
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private:
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std::string doGetName() const override;
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std::string doGetPrettyName(size_t indent) const override;
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SerializationPtr doGetDefaultSerialization() const override;
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};
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/// Check if conversion from from_type to to_type is Variant extension
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/// (both types are Variants and to_type contains all variants from from_type).
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bool isVariantExtension(const DataTypePtr & from_type, const DataTypePtr & to_type);
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}
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