ClickHouse/src/Parsers/ASTFunction.h
2021-06-16 21:10:07 +03:00

79 lines
2.5 KiB
C++

#pragma once
#include <Parsers/ASTWithAlias.h>
#include <Parsers/ASTExpressionList.h>
#include <Parsers/ASTSelectWithUnionQuery.h>
namespace DB
{
class ASTIdentifier;
/** AST for function application or operator.
*/
class ASTFunction : public ASTWithAlias
{
public:
String name;
ASTPtr arguments;
/// parameters - for parametric aggregate function. Example: quantile(0.9)(x) - what in first parens are 'parameters'.
ASTPtr parameters;
bool is_window_function = false;
// We have to make these fields ASTPtr because this is what the visitors
// expect. Some of them take const ASTPtr & (makes no sense), and some
// take ASTPtr & and modify it. I don't understand how the latter is
// compatible with also having an owning `children` array -- apparently it
// leads to some dangling children that are not referenced by the fields of
// the AST class itself. Some older code hints at the idea of having
// ownership in `children` only, and making the class fields to be raw
// pointers of proper type (see e.g. IAST::set), but this is not compatible
// with the visitor interface.
String window_name;
ASTPtr window_definition;
/// do not print empty parentheses if there are no args - compatibility with new AST for data types and engine names.
bool no_empty_args = false;
/** Get text identifying the AST node. */
String getID(char delim) const override;
ASTPtr clone() const override;
void updateTreeHashImpl(SipHash & hash_state) const override;
ASTSelectWithUnionQuery * tryGetQueryArgument() const;
ASTPtr toLiteral() const; // Try to convert functions like Array or Tuple to a literal form.
std::string getWindowDescription() const;
protected:
void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override;
void appendColumnNameImpl(WriteBuffer & ostr) const override;
void appendColumnNameImpl(WriteBuffer & ostr, const Settings & settings) const override;
private:
void appendColumnNameImpl(WriteBuffer & ostr, const Settings * settings) const;
};
template <typename... Args>
std::shared_ptr<ASTFunction> makeASTFunction(const String & name, Args &&... args)
{
auto function = std::make_shared<ASTFunction>();
function->name = name;
function->arguments = std::make_shared<ASTExpressionList>();
function->children.push_back(function->arguments);
function->arguments->children = { std::forward<Args>(args)... };
return function;
}
}