Inconsistency whether percentile iterators should return time

[andyfeller]

Bug report

System info: InfluxDB 1.1

Additional info:

Unsure whether this is actually a bug or not, however I noticed the inconsistency when I was trying to see how percentile() handles null or missing data. I thought it better to ask whether an issue than ignore it. Forgive for being unable to develop a process to confirm if an actual bug or not.

1. float percentile iterator returning time

/ NewFloatPercentileReduceSliceFunc returns the percentile value within a window.
func NewFloatPercentileReduceSliceFunc(percentile float64) FloatReduceSliceFunc {
	return func(a []FloatPoint) []FloatPoint {
		length := len(a)
		i := int(math.Floor(float64(length)*percentile/100.0+0.5)) - 1

		if i < 0 || i >= length {
			return nil
		}

		sort.Sort(floatPointsByValue(a))
		return []FloatPoint{{Time: a[i].Time, Value: a[i].Value, Aux: a[i].Aux}}
	}
}

2. integer percentile iterator returning ZeroTime

// NewIntegerPercentileReduceSliceFunc returns the percentile value within a window.
func NewIntegerPercentileReduceSliceFunc(percentile float64) IntegerReduceSliceFunc {
	return func(a []IntegerPoint) []IntegerPoint {
		length := len(a)
		i := int(math.Floor(float64(length)*percentile/100.0+0.5)) - 1

		if i < 0 || i >= length {
			return nil
		}

		sort.Sort(integerPointsByValue(a))
		return []IntegerPoint{{Time: ZeroTime, Value: a[i].Value, Aux: a[i].Aux}}
	}
}

[andyfeller]

Seems like this relates to #6292 commit hash 66a599825b7afaa031604b1ef5bfca5ef7a4c0e5 as only floats were update. @jsternberg thoughts?

[jsternberg]

That definitely looks like a bug. Percentile should be a selector for all types.

@jwilder should this fix target 1.1 or 1.2?