There comes a time in every DBA's life when they must disconnect a PostgreSQL client from the server; for us, that time is now. There are varying degrees of escalation available for this purpose, and several system catalog views to provide viable targets. Why would we want to forcefully cancel a query or disconnect a user?

To prevent utter havoc, should a user forget an important clause, a query could require several hours to complete. During this time, it is consuming an entire CPU and saturating the storage bandwidth while doing so. A buggy application could start a transaction and stop responding, leaving an idle transaction potentially holding locks and causing a wait backlog.

There are many reasons to evict a connection, and most of them revolve around maintaining a regular flow of queries. If we're unable to maintain low latency and high throughput, our work in building a highly available environment is wasted.