aggfuncs

type AggFunc interface {
	// AllocPartialResult allocates a specific data structure to store the
	// partial result, initializes it, and converts it to PartialResult to
	// return back. Aggregate operator implementation, no matter it's a hash
	// or stream, should hold this allocated PartialResult for the further
	// operations like: "ResetPartialResult", "UpdatePartialResult".
	AllocPartialResult() PartialResult

	// ResetPartialResult resets the partial result to the original state for a
	// specific aggregate function. It converts the input PartialResult to the
	// specific data structure which stores the partial result and then reset
	// every field to the proper original state.
	ResetPartialResult(pr PartialResult)

	// UpdatePartialResult updates the specific partial result for an aggregate
	// function using the input rows which all belonging to the same data group.
	// It converts the PartialResult to the specific data structure which stores
	// the partial result and then iterates on the input rows and update that
	// partial result according to the functionality and the state of the
	// aggregate function.
	UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error

	// MergePartialResult will be called in the final phase when parallelly
	// executing. It converts the PartialResult `src`, `dst` to the same specific
	// data structure which stores the partial results, and then evaluate the
	// final result using the partial results as input values.
	MergePartialResult(sctx sessionctx.Context, src, dst PartialResult) error

	// AppendFinalResult2Chunk finalizes the partial result and append the
	// final result to the input chunk. Like other operations, it converts the
	// input PartialResult to the specific data structure which stores the
	// partial result and then calculates the final result and append that
	// final result to the chunk provided.
	AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error
}

type PartialResult unsafe.Pointer

type SlidingWindowAggFunc interface {
	// Slide evaluates the aggregate functions using a sliding window. The input
	// lastStart and lastEnd are the interval of the former sliding window,
	// shiftStart, shiftEnd mean the sliding window offset. Note that the input
	// PartialResult stores the intermediate result which will be used in the next
	// sliding window, ensure call ResetPartialResult after a frame are evaluated
	// completely.
	Slide(sctx sessionctx.Context, rows []chunk.Row, lastStart, lastEnd uint64, shiftStart, shiftEnd uint64, pr PartialResult) error
}