FieldConfig: add interval to field config (#454)

* add interval to FieldConfig

* format

* Update data/field_config.go

Co-authored-by: Kyle Brandt <[email protected]>

Co-authored-by: Todd Treece <[email protected]>
Co-authored-by: Kyle Brandt <[email protected]>

Author: 3 people

data/arrow_test.go

@@ -239,6 +239,8 @@ func goldenDF() *data.Frame {
 			time.Unix(1568039450, 0),
 			time.Unix(0, maxEcma6Int),
 			time.Unix(0, math.MaxInt64),
+		}).SetConfig(&data.FieldConfig{
+			Interval: 1000,
 		}),
 		// Note: This is intentionally repeated to create a duplicate field.
 		data.NewField("timestamps", nil, []time.Time{

data/field_config.go

@@ -41,6 +41,12 @@ type FieldConfig struct {
 	Min      *ConfFloat64 `json:"min,omitempty"`      // is the maximum value of fields in the column. When present the frontend can skip the calculation.
 	Max      *ConfFloat64 `json:"max,omitempty"`      // see Min
 
+	// Interval indicates the expected regular step between values in the series.
+	// When an interval exists, consumers can identify "missing" values when the expected value is not present.
+	// The grafana timeseries visualization will render disconnected values when missing values are found it the time field.
+	// The interval uses the same units as the values.  For time.Time, this is defined in milliseconds.
+	Interval float64 `json:"interval,omitempty"`
+
 	// Convert input values into a display string
 	Mappings ValueMappings `json:"mappings,omitempty"`
 

data/testdata/all_types.golden.arrow

@@ -71,7 +71,7 @@
       },
       { "name": "bool_values", "type": "boolean", "typeInfo": { "frame": "bool" } },
       { "name": "nullable_bool_values", "type": "boolean", "typeInfo": { "frame": "bool", "nullable": true } },
-      { "name": "timestamps", "type": "time", "typeInfo": { "frame": "time.Time" } },
+      { "name": "timestamps", "type": "time", "typeInfo": { "frame": "time.Time" }, "config": { "interval": 1000 } },
       { "name": "timestamps", "type": "time", "typeInfo": { "frame": "time.Time" } },
       { "name": "nullable_timestamps", "type": "time", "typeInfo": { "frame": "time.Time", "nullable": true } }
     ]