Sample input data. Here is example input data for this scenario:

2018-10-10T01:10:11.322Z [ERROR] Invalid User ID. errorID=2, userId=10
2018-10-10T01:10:12.172Z [WARN]  Low Disk Space.
2018-10-10T01:10:14.122Z [ERROR] Invalid User ID. errorID=2, userId=11
2018-10-10T01:10:15.312Z [ERROR] Connection Dropped. errorID=112 server=120.100.121.12
2018-10-10T01:10:16.912Z [INFO]  User Login. userId=11

Query. To show a pie chart of the relative distribution of events with the respective log levels INFO, ERROR, and WARN, use the following query:

groupBy(logLevel)

If there is only one item in the pie chart, then the legend will not appear.