Query to find unique values for a label from a log stream

[devangshah97]

I am trying to find unique values for a label from a Log stream.

For eg, trying to find a unique users from the below stream.
Id:1 user:a
Id:2 user:b
Id:3 user:a
Id:4 user:c
Id:4 user:c

Would like the output as 3 or (a,b,c).

Appreciate any help. Thank you.