docs: migrating from influx (#2720)

Mention `-search.maxStalenessInterval` flag and its effect on query engine.

Signed-off-by: hagen1778 <roman@victoriametrics.com>
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Roman Khavronenko 2022-06-14 09:10:44 +02:00 committed by Aliaksandr Valialkin
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@ -196,11 +196,16 @@ Grafana will have the following form:
{% include img.html href="migrate-from-influx-data-sample-in-vm.png" %} {% include img.html href="migrate-from-influx-data-sample-in-vm.png" %}
It is noticeable that visualizations from both databases are a bit different - VictoriaMetrics shows some extra points Visualizations from both databases are a bit different - VictoriaMetrics shows some extra points
filling the gaps in the graph. This behavior is described in more filling the gaps in the graph. This behavior is described in more
detail [here](https://docs.victoriametrics.com/keyConcepts.html#range-query). In InfluxDB, we can achieve a similar detail [here](https://docs.victoriametrics.com/keyConcepts.html#range-query). In InfluxDB, we can achieve a similar
behavior by adding `fill(previous)` to the query. behavior by adding `fill(previous)` to the query.
VictoriaMetrics fills the gaps on the graph assuming time series are always continious and not discrete.
To limit the interval on which VictoriaMetrics will try to fill the gaps try setting `-search.maxStalenessInterval`
command-line flag to the value equal to actual resolution between data points (for example, to `1ms`).
### Advanced usage ### Advanced usage
The good thing is that knowing the basics and some aggregation functions is often enough for using MetricsQL or PromQL. The good thing is that knowing the basics and some aggregation functions is often enough for using MetricsQL or PromQL.