[v3] InfluxDB 3.5 performance seems worse than InfluxDB 1.7 for `show tag values`

[caiqinwei26-byte]

he performance of InfluxDB 3.5 seems to be worse than that of InfluxDB 1.7. For example:

SHOW TAG VALUES FROM "metric_name" WITH KEY =~ /^tag_key$/ WHERE time > now() - 3d

If we use the DVC cache, it's equivalent to storing the dimensions in memory, which can lead to memory explosion issues.

[philjb]

Hi @caiqinwei26-byte -- do you have a sample dataset you can share that demonstrates the performance you are seeing? The line protocol files for example?

[pauldix]

This is going to be an expensive query in v3. That's because we currently don't keep an index of the tag values. The benefit of this is that cardinality doesn't cause the server to blow up. The drawback is that queries like this are much, much slower.

Currently, the only way to make this faster is to reduce the time bound on the query so it doesn't have to scan as much data.