ClickHouse/src/Interpreters/AggregateDescription.h

#pragma once

#include <AggregateFunctions/IAggregateFunction.h>
#include <DataTypes/IDataType.h>
#include <Core/ColumnNumbers.h>
#include <Core/Names.h>
#include <Core/SortDescription.h>
#include <Parsers/IAST_fwd.h>


namespace DB
{

class ASTFunction;

struct AggregateDescription
{
    AggregateFunctionPtr function;
    Array parameters;        /// Parameters of the (parametric) aggregate function.
    ColumnNumbers arguments;
    Names argument_names;    /// used if no `arguments` are specified.
    String column_name;      /// What name to use for a column with aggregate function values

    void explain(WriteBuffer & out, size_t indent) const; /// Get description for EXPLAIN query.
};

using AggregateDescriptions = std::vector<AggregateDescription>;


struct WindowFunctionDescription
{
    // According to the standard, a window function can refer to a window declared
    // elsewhere, using its name. We haven't implemented this yet: all windows
    // are declared in OVER clause, but they still get an auto-generated name,
    // and this name is used to find the window that corresponds to a function.
    std::string window_name;

    std::string column_name;
    const ASTFunction * function_node;
    AggregateFunctionPtr aggregate_function;
    Array function_parameters;
    DataTypes argument_types;
    Names argument_names;

    std::string dump() const;
};

struct WindowDescription
{
    std::string window_name;

    // We don't care about the particular order of keys for PARTITION BY, only
    // that they are sorted. For now we always require ASC, but we could be more
    // flexible and match any direction, or even different order of columns.
    SortDescription partition_by;

    SortDescription order_by;

    // To calculate the window function, we sort input data first by PARTITION BY,
    // then by ORDER BY. This field holds this combined sort order.
    SortDescription full_sort_description;

    // No frame info as of yet.

    std::string dump() const;
};

using WindowFunctionDescriptions = std::vector<WindowFunctionDescription>;

using WindowDescriptions = std::unordered_map<std::string, WindowDescription>;

}