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#pragma once
#include <Core/Field.h>
#include <Parsers/ASTWithAlias.h>
#include <Parsers/TokenIterator.h>
#include <Common/FieldVisitorDump.h>
#include <optional>
namespace DB
{
/// Literal (atomic) - number, string, NULL
class ASTLiteral : public ASTWithAlias
{
public:
explicit ASTLiteral(Field value_) : value(std::move(value_)) {}
Field value;
/// For ConstantExpressionTemplate
std::optional<TokenIterator> begin;
std::optional<TokenIterator> end;
/*
* The name of the column corresponding to this literal. Only used to
* disambiguate the literal columns with the same display name that are
* created at the expression analyzer stage. In the future, we might want to
* have a full separation between display names and column identifiers. For
* now, this field is effectively just some private EA data.
*/
String unique_column_name;
/// For compatibility reasons in distributed queries,
/// we may need to use legacy column name for tuple literal.
bool use_legacy_column_name_of_tuple = false;
/** Get the text that identifies this element. */
String getID(char delim) const override { return "Literal" + (delim + applyVisitor(FieldVisitorDump(), value)); }
ASTPtr clone() const override;
void updateTreeHashImpl(SipHash & hash_state) const override;
protected:
void formatImplWithoutAlias(const FormatSettings & settings, FormatState &, FormatStateStacked) const override;
void appendColumnNameImpl(WriteBuffer & ostr) const override;
private:
/// Legacy version of 'appendColumnNameImpl'. It differs only with tuple literals.
/// It's only needed to continue working of queries with tuple literals
/// in distributed tables while rolling update.
void appendColumnNameImplLegacy(WriteBuffer & ostr) const;
};
}
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