Nested structures are not common in Relational Database Management Systems. Usually, it’s just flat tables. Sometimes it would be convenient to store unstructured information in structured databases.
We are working to adapt ClickHouse as a long term storage for Percona Monitoring and Management (PMM), and particularly to store detailed information about queries. One of the problems we are trying to solve is to count the different errors that cause a particular query to fail.
For example, for date 2017-08-17 the query:
"SELECT foo FROM bar WHERE …[Read more]