Support for subsecond intervals

[oplehto]

It seems that it's not possible to have sub-second precision on graphs. This looks like it's due to a hard limit of 1 second for the $timeSeries macro:
https://github.com/Vertamedia/clickhouse-grafana/blob/2f2d2e164848ac0c54d745ab8d7ec301dc2c948a/src/sql_query.ts#L530-L532

A workaround is to use $__interval_ms instead of $interval. For example:

(intDiv(toFloat64("_time") * 1000, $__interval_ms) * $__interval_ms) AS t,

Adding support for $interval to be < 1 would be handy but it might have some side-effects I didn't check for. Thus it may make more sense to change the $timeSeries to use $__interval_ms here:

https://github.com/Vertamedia/clickhouse-grafana/blob/2f2d2e164848ac0c54d745ab8d7ec301dc2c948a/src/sql_query.ts#L467

[Slach]

I think we can apply $__interval_ms

[Slach]

@oplehto you can't select subsecond interval from grafana itself in range queries widget, so i not sure how it can be applicable

currently we implements $timeFilter64ByColumn which will release on 2.4.0

[Slach]

@oplehto could you provide more use-cases for your proposal?

[oplehto]

@Slach It is possible to zoom into sub-second data ranges and we have data that has sub-second intervals. I don't understand what would

Others seem to have this issue as well #398