Does cardinality in one measurement affect another?


Simple question really. I have a database. In this database are two measurements, measurementA and measurementB. Both measurements have the same tags, tagA and tagB. Now, suppose measurementA has 100000 points with lots of varying tag values, causing a very high cardinality. At the same time, measurementB has only 100 points with only a couple of tag values and very low cardinality.

My question: does the cardinality of measurementA influence query speed (specifically SELECT queries) on measurementB in any way?


@Basman It will affect query speed somewhat. Currently we store all series keys (measurement, tag key, tag value, combinations) in an in memory index. The size of this index affects RAM usage which can affect query speed. However I don’t expect that to make queries on the lower cardinality measurement much slower. This answer will change with the introduction of the Time Series Index in the next release as the index will be partially on disk.

1 Like