ClickHouse is an open-source column-oriented OLAP database that excels in analytical queries due to its column-store architecture, whereas PostgreSQL is a relational database focused on extensibility and SQL compliance. The two databases complement each other, with ClickHouse suited for real-time analytics and Postgres ideal for transactional use cases. By leveraging the `postgresql` function or table engine in ClickHouse, users can push queries down to Postgres and exploit its indexes, while also utilizing ClickHouse's MergeTree tables for faster analytical queries. The performance difference between direct execution on Postgres versus using ClickHouse is significant, especially when exploiting primary keys and file system caches. With proper optimization, ClickHouse clearly outperforms PostgreSQL in linear scans and analytical-type queries.