Merge pull request #7937 from influxdata/js-7895-incorrect-calculations-math-with-aggregates

Fix incorrect math when aggregates that emit different times are used

CHANGELOG.md

@@ -7,6 +7,7 @@
 - [#7910](https://github.com/influxdata/influxdb/issues/7910): Fix EvalType when a parenthesis expression is used.
 - [#7929](https://github.com/influxdata/influxdb/issues/7929): Fix series tag iteration segfault. (#7922)
 - [#7906](https://github.com/influxdata/influxdb/issues/7906): Anchors not working as expected with case-insensitive regex
+- [#7895](https://github.com/influxdata/influxdb/issues/7895): Fix incorrect math when aggregates that emit different times are used.
 
 ## v1.2.0 [2017-01-24]
 

cmd/influxd/run/server_test.go

@@ -1684,6 +1684,15 @@ func TestServer_Query_SelectGroupByTimeDerivative(t *testing.T) {
 cpu value=15 1278010021000000000
 cpu value=20 1278010022000000000
 cpu value=25 1278010023000000000
+
+cpu0,host=server01 ticks=10,total=100 1278010020000000000
+cpu0,host=server01 ticks=30,total=100 1278010021000000000
+cpu0,host=server01 ticks=32,total=100 1278010022000000000
+cpu0,host=server01 ticks=47,total=100 1278010023000000000
+cpu0,host=server02 ticks=40,total=100 1278010020000000000
+cpu0,host=server02 ticks=45,total=100 1278010021000000000
+cpu0,host=server02 ticks=84,total=100 1278010022000000000
+cpu0,host=server02 ticks=101,total=100 1278010023000000000
 `)},
 	}
 
@@ -1789,6 +1798,11 @@ cpu value=25 1278010023000000000
 			command: `SELECT derivative(percentile(value, 50), 4s) from db0.rp0.cpu where time >= '2010-07-01 18:47:00' and time <= '2010-07-01 18:47:03' group by time(2s)`,
 			exp:     `{"results":[{"statement_id":0,"series":[{"name":"cpu","columns":["time","derivative"],"values":[["2010-07-01T18:47:02Z",20]]}]}]}`,
 		},
+		&Query{
+			name:    "calculate derivative of ticks divided by aggregate",
+			command: `SELECT non_negative_derivative(mean(ticks), 1s) / last(total) * 100 AS usage FROM db0.rp0.cpu0 WHERE time >= '2010-07-01 18:47:00' AND time <= '2010-07-01 18:47:03' GROUP BY host, time(1s)`,
+			exp:     `{"results":[{"statement_id":0,"series":[{"name":"cpu0","tags":{"host":"server01"},"columns":["time","usage"],"values":[["2010-07-01T18:47:00Z",null],["2010-07-01T18:47:01Z",20],["2010-07-01T18:47:02Z",2],["2010-07-01T18:47:03Z",15]]},{"name":"cpu0","tags":{"host":"server02"},"columns":["time","usage"],"values":[["2010-07-01T18:47:00Z",null],["2010-07-01T18:47:01Z",5],["2010-07-01T18:47:02Z",39],["2010-07-01T18:47:03Z",17]]}]}]}`,
+		},
 	}...)
 
 	for i, query := range test.queries {

influxql/iterator.gen.go.tmpl

@@ -1259,30 +1259,10 @@ func (itr *{{$k.name}}{{if ne $k.Name $v.Name}}{{$v.Name}}{{end}}ExprIterator) C
 
 func (itr *{{$k.name}}{{if ne $k.Name $v.Name}}{{$v.Name}}{{end}}ExprIterator) Next() (*{{$v.Name}}Point, error) {
 	for {
-		a, err := itr.left.Next()
-		if err != nil {
+		a, b, err := itr.next()
+		if err != nil || (a == nil && b == nil) {
 			return nil, err
 		}
-		b, err := itr.right.Next()
-		if err != nil {
-			return nil, err
-		}
-
-		if a == nil && b == nil {
-			return nil, nil
-		} else if itr.points == nil && (a == nil || b == nil ) {
-			return nil, nil
-		}
-
-		if a != nil && b != nil {
-			if a.Time > b.Time {
-				itr.left.unread(a)
-				a = nil
-			} else if a.Time < b.Time {
-				itr.right.unread(b)
-				b = nil
-			}
-		}
 
 		if a == nil || a.Nil {
 			if itr.points == nil {
@@ -1336,6 +1316,48 @@ func (itr *{{$k.name}}{{if ne $k.Name $v.Name}}{{$v.Name}}{{end}}ExprIterator) N
 	}
 }
 
+// next returns the next points within each iterator. If the iterators are
+// uneven, it organizes them so only matching points are returned.
+func (itr *{{$k.name}}{{if ne $k.Name $v.Name}}{{$v.Name}}{{end}}ExprIterator) next() (a, b *{{$k.Name}}Point, err error) {
+	// Retrieve the next value for both the left and right.
+	a, err = itr.left.Next()
+	if err != nil {
+		return nil, nil, err
+	}
+	b, err = itr.right.Next()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// If we have a point from both, make sure that they match each other.
+	if a != nil && b != nil {
+		if a.Name > b.Name {
+			itr.left.unread(a)
+			return nil, b, nil
+		} else if a.Name < b.Name {
+			itr.right.unread(b)
+			return a, nil, nil
+		}
+
+		if ltags, rtags := a.Tags.ID(), b.Tags.ID(); ltags > rtags {
+			itr.left.unread(a)
+			return nil, b, nil
+		} else if ltags < rtags {
+			itr.right.unread(b)
+			return a, nil, nil
+		}
+
+		if a.Time > b.Time {
+			itr.left.unread(a)
+			return nil, b, nil
+		} else if a.Time < b.Time {
+			itr.right.unread(b)
+			return a, nil, nil
+		}
+	}
+	return a, b, nil
+}
+
 // {{$k.name}}{{if ne $k.Name $v.Name}}{{$v.Name}}{{end}}ExprFunc creates or modifies a point by combining two
 // points. The point passed in may be modified and returned rather than
 // allocating a new point if possible. One of the points may be nil, but at