Our billing pipeline was suddenly slow. The culprit was a hidden bottleneck in ClickHouse

This post details the debugging and resolution of performance degradation in the Ready-Analytics ClickHouse cluster due to increased data part counts following a migration to a new partitioning scheme. Three patches were developed and contributed upstream to address lock contention during query planning (using shared locks instead of exclusive locks), vector copying (deferring the copy and creating a shared copy), and to improve part filtering efficiency (binary search for parts).