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109 lines
3.3 KiB
C++
109 lines
3.3 KiB
C++
#pragma once
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#include <Core/Field.h>
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#include <Parsers/IAST_fwd.h>
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#include <AggregateFunctions/IAggregateFunction.h>
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#include <Core/SortDescription.h>
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#include <DataTypes/IDataType.h>
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#include <Core/Names.h>
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#include <Core/Types.h>
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namespace DB
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{
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class ASTFunction;
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struct WindowFunctionDescription
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{
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std::string column_name;
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const ASTFunction * function_node = nullptr;
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AggregateFunctionPtr aggregate_function;
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Array function_parameters;
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DataTypes argument_types;
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Names argument_names;
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std::string dump() const;
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};
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struct WindowFrame
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{
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enum class FrameType { Rows, Groups, Range };
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enum class BoundaryType { Unbounded, Current, Offset };
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// This flag signifies that the frame properties were not set explicitly by
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// user, but the fields of this structure still have to contain proper values
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// for the default frame of RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW.
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bool is_default = true;
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FrameType type = FrameType::Range;
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// UNBOUNDED FOLLOWING for the frame end is forbidden by the standard, but for
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// uniformity the begin_preceding still has to be set to true for UNBOUNDED
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// frame start.
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// Offset might be both preceding and following, controlled by begin_preceding,
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// but the offset value must be positive.
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BoundaryType begin_type = BoundaryType::Unbounded;
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Field begin_offset = 0;
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bool begin_preceding = true;
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// Here as well, Unbounded can only be UNBOUNDED FOLLOWING, and end_preceding
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// must be false.
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BoundaryType end_type = BoundaryType::Current;
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Field end_offset = 0;
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bool end_preceding = false;
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// Throws BAD_ARGUMENTS exception if the frame definition is incorrect, e.g.
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// the frame start comes later than the frame end.
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void checkValid() const;
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std::string toString() const;
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void toString(WriteBuffer & buf) const;
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bool operator == (const WindowFrame & other) const
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{
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// We don't compare is_default because it's not a real property of the
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// frame, and only influences how we display it.
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return other.type == type
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&& other.begin_type == begin_type
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&& other.begin_offset == begin_offset
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&& other.begin_preceding == begin_preceding
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&& other.end_type == end_type
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&& other.end_offset == end_offset
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&& other.end_preceding == end_preceding
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;
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}
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};
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struct WindowDescription
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{
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std::string window_name;
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// We don't care about the particular order of keys for PARTITION BY, only
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// that they are sorted. For now we always require ASC, but we could be more
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// flexible and match any direction, or even different order of columns.
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SortDescription partition_by;
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SortDescription order_by;
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// To calculate the window function, we sort input data first by PARTITION BY,
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// then by ORDER BY. This field holds this combined sort order.
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SortDescription full_sort_description;
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WindowFrame frame;
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// The window functions that are calculated for this window.
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std::vector<WindowFunctionDescription> window_functions;
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std::string dump() const;
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void checkValid() const;
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};
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using WindowFunctionDescriptions = std::vector<WindowFunctionDescription>;
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using WindowDescriptions = std::unordered_map<std::string, WindowDescription>;
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}
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