Numeric fields only when using numeric aggregates

influxql/functions.go

@@ -749,6 +749,16 @@ func ReducePercentile(percentile float64) ReduceFunc {
 	}
 }
 
+// IsNumeric returns whether a given aggregate can only be run on numeric fields.
+func IsNumeric(c *Call) bool {
+	switch c.Name {
+	case "count", "first", "last":
+		return false
+	default:
+		return true
+	}
+}
+
 // MapRawQuery is for queries without aggregates
 func MapRawQuery(itr Iterator) interface{} {
 	var values []*rawQueryMapOutput

tx.go

@@ -93,6 +93,21 @@ func (tx *tx) CreateMapReduceJobs(stmt *influxql.SelectStatement, tagKeys []stri
 			}
 		}
 
+		// If a numerical aggregate is requested, ensure it is only performed on numeric data.
+		for _, a := range stmt.FunctionCalls() {
+			lit, ok := a.Args[0].(*influxql.VarRef)
+			if !ok {
+				return nil, fmt.Errorf("aggregate call didn't contain a field %s", a.String())
+			}
+			if influxql.IsNumeric(a) {
+				f := m.FieldByName(lit.Val)
+				if f.Type != influxql.Float && f.Type != influxql.Integer {
+					return nil, fmt.Errorf("aggregate '%s' requires numerical field values. Field '%s' is of type %s",
+						a.Name, f.Name, f.Type)
+				}
+			}
+		}
+
 		// Grab time range from statement.
 		tmin, tmax := influxql.TimeRange(stmt.Condition)
 		if tmax.IsZero() {