Avg with quantile_over_time throws an error

[prajon84]

Describe the bug When building LogQL queries that contain avg by (...) (quantile_over_time(....) throws an error as: SelectSamples unimplemented: the query-frontend cannot evaluate an expression that selects samples. this is likely a bug in the query engine. please contact your system operator

To Reproduce Steps to reproduce the behavior:

1. Using hosted Grafana Loki
2. Any query (in dashboard or explore)
3. Query: avg by(service) (quantile_over_time(0.75, {service="<service_name>"} | json | unwrap attributes_measurement_value [5m]))

receive SelectSamples unimplemented: the query-frontend cannot evaluate an expression that selects samples. this is likely a bug in the query engine. please contact your system operator

Expected behavior Avg by(...) (quantile_over_time(...)) should work.

Environment: Hosted

Screenshots, Promtail config, or terminal output .

[prajon84]

cc: @chaudum