Fix: Allow null data points for time series

[kevinwcyu]

Currently, if a column includes TimeSeriesMeasureValueColumnInfo we assume that it also has a time series value

timestream-datasource/pkg/timestream/helper.go

Lines 39 to 53 in 7f68a0b

	hasTimeseries = true
	} else {
	builders = append(builders, b)
	}
	}
	if hasTimeseries {
	// Each row is a new series
	for _, timeseriesColumn := range timeseriesColumns {
	for _, series := range res.Rows {
	tv := series.Data[timeseriesColumn.columnIdx].TimeSeriesValue
	if tv == nil {
	dr.Error = fmt.Errorf("Expecting timeseries colum at: %d", timeseriesColumn.columnIdx)
	return
	}

However, it could just be a null data point.

This PR allows data points to be a null value instead of assuming it must be present.

This fixes #168. You can see a screenshot of what the error looked like in the panel in the linked issue.

Currently this is what the Timestream query editor shows when there are null data points.

With the changes in this PR this is what Grafana looks like now

[github-actions]

Code coverage report for PR #170

	Go	TypeScript
main	64.8%	47.49%
PR	64.9%	47.49%
difference	.1%	0%

[sunker]

Nice work!

[andresmgot]

nice, I see you figured out how these integration tests work :)

[andresmgot]

you need to check if the pointer is null to avoid a possible panic

[kevinwcyu]

oof, nice catch.

[brunoleite]

Grafana shows "No Data" for this scenario when using influx db instead of an empty graph. I tried to replicate the same behavior with timestream, but I did not manage to do it.

[kevinwcyu]

Grafana shows "No Data" for this scenario when using influx db instead of an empty graph. I tried to replicate the same behavior with timestream, but I did not manage to do it.

@brunoleite, if you use the following

SELECT interpolatedValue
FROM interpolatedTimeseries
WHERE interpolatedValue IS NOT NULL

instead of

SELECT *
FROM interpolatedTimeseries

It should not return any rows and will show "No Data".

[brunoleite]

Sorry for the delay. I have tried that (without this fix), and if I add WHERE interpolatedValue IS NOT NULL I only see a black graph, without the red badge.

Some times I also see: