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#pragma once
#include <Parsers/IAST.h>
namespace DB
{
/** Base class for AST, which can contain an alias (identifiers, literals, functions).
*/
class ASTWithAlias : public IAST
{
public:
/// The alias, if any, or an empty string.
String alias;
/// If is true, getColumnName returns alias. Uses for aliases in former WITH section of SELECT query.
/// Example: 'WITH pow(2, 2) as a SELECT pow(a, 2)' returns 'pow(a, 2)' instead of 'pow(pow(2, 2), 2)'
bool prefer_alias_to_column_name = false;
using IAST::IAST;
void appendColumnName(WriteBuffer & ostr) const final;
void appendColumnNameWithoutAlias(WriteBuffer & ostr) const final;
String getAliasOrColumnName() const override { return alias.empty() ? getColumnName() : alias; }
String tryGetAlias() const override { return alias; }
void setAlias(const String & to) override { alias = to; }
/// Calls formatImplWithoutAlias, and also outputs an alias. If necessary, encloses the entire expression in brackets.
void formatImpl(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override final;
virtual void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const = 0;
protected:
virtual void appendColumnNameImpl(WriteBuffer & ostr) const = 0;
};
/// helper for setting aliases and chaining result to other functions
inline ASTPtr setAlias(ASTPtr ast, const String & alias)
{
ast->setAlias(alias);
return ast;
}
}
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