I loaded example ontime dataset and created a materialized view with the following definition:

CREATE MATERIALIZED VIEW basic ENGINE = AggregatingMergeTree(FlightDate, Carrier, 8192) AS
SELECT
    FlightDate,
    Carrier,
    uniqState(FlightNum) AS Users
FROM ontime
GROUP BY
    FlightDate,
    Carrier

Then I inserted data to ontime database and tried to query basic table with SELECT * FROM basic LIMIT 10 via the clickhouse-client

The output of the query is:

Exception on client:
Code: 89. DB::Exception: QuickLZ compression method is disabled: while receiving packet from localhost:9000, ::1

The problem is that I try to fetch the aggregation state stored in User column. I can execute the following query successfully: select uniqMerge(Users) from basic since the output of uniqMerge is a numeric value. I think the server should throw a more descriptive error or return the aggregation state as binary type.