ClickHouse/dbms/include/DB/Parsers/ASTFunction.h

#pragma once

#include <DB/Parsers/ASTWithAlias.h>
#include <DB/Parsers/ASTExpressionList.h>


namespace DB
{

/** AST for function application or operator.
  */
class ASTFunction : public ASTWithAlias
{
public:
    /// TODO This is semantic, not syntax. Remove it.
    enum FunctionKind
    {
        UNKNOWN,
        TABLE_FUNCTION,
        FUNCTION,
        AGGREGATE_FUNCTION,
        LAMBDA_EXPRESSION,
        ARRAY_JOIN,
    };

    String name;
    ASTPtr arguments;
    /// parameters - for parametric aggregate function. Example: quantile(0.9)(x) - what in first parens are 'parameters'.
    ASTPtr parameters;

    FunctionKind kind{UNKNOWN};

public:
    ASTFunction() = default;
    ASTFunction(const StringRange range_) : ASTWithAlias(range_) {}

    String getColumnName() const override;

    /** Get text identifying the AST node. */
    String getID() const override;

    ASTPtr clone() const override;

protected:
    void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override;
};


template <typename... Args>
ASTPtr makeASTFunction(const String & name, Args &&... args)
{
    const auto function = std::make_shared<ASTFunction>();
    ASTPtr result{function};

    function->name = name;
    function->arguments = std::make_shared<ASTExpressionList>();
    function->children.push_back(function->arguments);

    function->arguments->children = { std::forward<Args>(args)... };

    return result;
}


template <typename... Args>
ASTPtr makeASTFunction(const String & name, const StringRange & function_range,
    const StringRange & arguments_range, Args &&... args)
{
    const auto function = std::make_shared<ASTFunction>(function_range);
    ASTPtr result{function};

    function->name = name;
    function->arguments = std::make_shared<ASTExpressionList>(arguments_range);
    function->children.push_back(function->arguments);

    function->arguments->children = { std::forward<Args>(args)... };

    return result;
}

}