Creating Grafana Variables with MongoDB Query

Question

I have some problems with mongodb query..

I will give an example with sql query and I want to write that with mongo db query in Grafana. Grafana supports mongo db 'find' and 'aggregate'.

table name = flow , column name = level

sql query example 1;

select distinc level from flow

mongo db query: ?

sql query example 2 ;

select * from flow where level = 'error'

mongo db query: ?

Thanks for your help.