Cardinality

wikipedia:Cardinality is generally defined as the number of elements in a set.

Calculating the exact cardinality of a multiset requires an amount of memory proportional to the cardinality, which is impractical for very large data sets. The HyperLogLog algorithm is able to estimate cardinalities of > 109 with a typical accuracy (standard error) of 2%, using 1.5 kB of memory.

You can have lower cardinality (1:5 label-value ratio), standard cardinality (1:80 label-value ratio), or high cardinality (1:10,000 label-value ratio).

NRQL

FROM Metric SELECT cardinality(metric.name) SINCE today RAW

• Metrics
• High cardinality
• HyperLogLog, HyperLogLog++
• Infinite set, Multiset

Activities

• Read about cardinality aggregation in Elasticsearch https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-cardinality-aggregation.html
• Read https://docs.newrelic.com/docs/data-apis/ingest-apis/metric-api/NRQL-high-cardinality-metrics/ to understand "What metric is contributing the most cardinality?" and "What impact does a given attribute(s) have to that total cardinality?".
• Prometheus https://www.robustperception.io/cardinality-is-key/

Related

• Elasticsearch
• New Relic

See also

• Cardinality, cortex-tools

https://grafana.com/blog/2022/02/15/what-are-cardinality-spikes-and-why-do-they-matter/