docs: mention streaming aggregation as way to reduce cardinality

Signed-off-by: hagen1778 <roman@victoriametrics.com>

README.md

@@ -1668,7 +1668,8 @@ Retention filters can be evaluated for free by downloading and using enterprise
 
 * `-downsampling.period=30d:5m,180d:1h` instructs VictoriaMetrics to deduplicate samples older than 30 days with 5 minutes interval and to deduplicate samples older than 180 days with 1 hour interval.
 
-Downsampling is applied independently per each time series. It can reduce disk space usage and improve query performance if it is applied to time series with big number of samples per each series. The downsampling doesn't improve query performance if the database contains big number of time series with small number of samples per each series (aka [high churn rate](https://docs.victoriametrics.com/FAQ.html#what-is-high-churn-rate)), since downsampling doesn't reduce the number of time series. So the majority of time is spent on searching for the matching time series. It is possible to use recording rules in [vmalert](https://docs.victoriametrics.com/vmalert.html) in order to reduce the number of time series. See [these docs](https://docs.victoriametrics.com/vmalert.html#downsampling-and-aggregation-via-vmalert).
+Downsampling is applied independently per each time series. It can reduce disk space usage and improve query performance if it is applied to time series with big number of samples per each series. The downsampling doesn't improve query performance if the database contains big number of time series with small number of samples per each series (aka [high churn rate](https://docs.victoriametrics.com/FAQ.html#what-is-high-churn-rate)), since downsampling doesn't reduce the number of time series. So the majority of time is spent on searching for the matching time series. 
+It is possible to use [stream aggregation](https://docs.victoriametrics.com/stream-aggregation.html) in vmagent or recording rules in [vmalert](https://docs.victoriametrics.com/vmalert.html) in order to [reduce the number of time series](https://docs.victoriametrics.com/vmalert.html#downsampling-and-aggregation-via-vmalert).
 
 Downsampling happens during [background merges](https://docs.victoriametrics.com/#storage) 
 and can't be performed if there is not enough of free disk space or if vmstorage 

docs/README.md

@@ -1671,7 +1671,8 @@ Retention filters can be evaluated for free by downloading and using enterprise
 
 * `-downsampling.period=30d:5m,180d:1h` instructs VictoriaMetrics to deduplicate samples older than 30 days with 5 minutes interval and to deduplicate samples older than 180 days with 1 hour interval.
 
-Downsampling is applied independently per each time series. It can reduce disk space usage and improve query performance if it is applied to time series with big number of samples per each series. The downsampling doesn't improve query performance if the database contains big number of time series with small number of samples per each series (aka [high churn rate](https://docs.victoriametrics.com/FAQ.html#what-is-high-churn-rate)), since downsampling doesn't reduce the number of time series. So the majority of time is spent on searching for the matching time series. It is possible to use recording rules in [vmalert](https://docs.victoriametrics.com/vmalert.html) in order to reduce the number of time series. See [these docs](https://docs.victoriametrics.com/vmalert.html#downsampling-and-aggregation-via-vmalert).
+Downsampling is applied independently per each time series. It can reduce disk space usage and improve query performance if it is applied to time series with big number of samples per each series. The downsampling doesn't improve query performance if the database contains big number of time series with small number of samples per each series (aka [high churn rate](https://docs.victoriametrics.com/FAQ.html#what-is-high-churn-rate)), since downsampling doesn't reduce the number of time series. So the majority of time is spent on searching for the matching time series. 
+It is possible to use [stream aggregation](https://docs.victoriametrics.com/stream-aggregation.html) in vmagent or recording rules in [vmalert](https://docs.victoriametrics.com/vmalert.html) in order to [reduce the number of time series](https://docs.victoriametrics.com/vmalert.html#downsampling-and-aggregation-via-vmalert).
 
 Downsampling happens during [background merges](https://docs.victoriametrics.com/#storage) 
 and can't be performed if there is not enough of free disk space or if vmstorage 

docs/Single-server-VictoriaMetrics.md

@@ -1679,7 +1679,8 @@ Retention filters can be evaluated for free by downloading and using enterprise
 
 * `-downsampling.period=30d:5m,180d:1h` instructs VictoriaMetrics to deduplicate samples older than 30 days with 5 minutes interval and to deduplicate samples older than 180 days with 1 hour interval.
 
-Downsampling is applied independently per each time series. It can reduce disk space usage and improve query performance if it is applied to time series with big number of samples per each series. The downsampling doesn't improve query performance if the database contains big number of time series with small number of samples per each series (aka [high churn rate](https://docs.victoriametrics.com/FAQ.html#what-is-high-churn-rate)), since downsampling doesn't reduce the number of time series. So the majority of time is spent on searching for the matching time series. It is possible to use recording rules in [vmalert](https://docs.victoriametrics.com/vmalert.html) in order to reduce the number of time series. See [these docs](https://docs.victoriametrics.com/vmalert.html#downsampling-and-aggregation-via-vmalert).
+Downsampling is applied independently per each time series. It can reduce disk space usage and improve query performance if it is applied to time series with big number of samples per each series. The downsampling doesn't improve query performance if the database contains big number of time series with small number of samples per each series (aka [high churn rate](https://docs.victoriametrics.com/FAQ.html#what-is-high-churn-rate)), since downsampling doesn't reduce the number of time series. So the majority of time is spent on searching for the matching time series. 
+It is possible to use [stream aggregation](https://docs.victoriametrics.com/stream-aggregation.html) in vmagent or recording rules in [vmalert](https://docs.victoriametrics.com/vmalert.html) in order to [reduce the number of time series](https://docs.victoriametrics.com/vmalert.html#downsampling-and-aggregation-via-vmalert).
 
 Downsampling happens during [background merges](https://docs.victoriametrics.com/#storage) 
 and can't be performed if there is not enough of free disk space or if vmstorage