return fmt.Errorf("%s() requires a numeric argument", fnStr)
	}
	errInvalidAggregation = errors.New("Invalid aggregation seen")
)

type aggVal struct {
	runningSum             *Value
	runningCount           int64
	runningMax, runningMin *Value

	// Stores if at least one record has been seen
	seen bool
}

func newAggVal(fn FuncName) *aggVal {
	switch fn {
	case aggFnAvg, aggFnSum: