The query returns the correct answer but causes a ClickHouse cluster spike — no error appeared. Why?
The silent failure is cost invisibility. A valid query scanned an unbounded time range or bypassed partition pruning, so ClickHouse completed it while consuming substantial CPU, network, or disk. The engineering fix is to enforce max_bytes_to_read and max_execution_time, require partition predicates, inspect read_rows and read_bytes, and route exploratory work to a replica or isolated workload.
How does ClickHouse MCP compare with PostgreSQL MCP?
ClickHouse is optimized for large analytical scans, aggregations, and event data; PostgreSQL is optimized for transactional workloads, relational integrity, and general application state. Use ClickHouse for OLAP and observability analytics, and Postgres for OLTP and application records.
Can it modify tables or run DDL?
Only when the configured credentials and server expose those operations. Production agents should use read-only roles and reviewed migration pipelines for schema changes.
Why do results differ from a dashboard?
The dashboard may query a materialized view, use a different timezone, apply hidden filters, or read a different cluster. Reproduce its exact SQL, datasource, time window, and timezone before comparing results.