Definitions

Definitions

When it comes to timeseries data, there are lots of terms tossed about that can lead to some confusion. This page is a sort of glossary that helps to define words related to the use of OpenTSDB.

Cardinality

Cardinality is a mathematical term defined as the number of elements in a set. In database lingo, it's often used to refer to the number of unique items in an index. With regards to OpenTSDB it can refer to:

• The number of unique time series for a given metric
• The number of unique tag values associated with a tag name

Due to the nature of the OpenTSDB storage schema, metrics with higher cardinality may take longer return results during query execution than those with lower cardinality. E.g. we may have metric foo with the tag name datacenter and there are