Postgres Hacking 101: \watch with limited loops

session summary

The main exercise added a maximum iteration count to psql's backslash-watch command, allowing monitoring or sampling queries to stop automatically. Parsing a second optional argument exposed subtleties in psql's meta-command scanner, whitespace handling, defaults, and preserving unlimited behavior; the live prototype was close but still malfunctioned and needed offline cleanup before its later upstream completion. The final segment reviewed a proposed pg_stat_session view, questioning its per-backend memory and runtime overhead, missing functional tests, and practical value to DBAs.

timecodes

1. 00:30 Use case for a bounded psql watch
2. 05:00 ULID work shifts toward UUIDv7
3. 10:00 Starting the psql meta-command patch
4. 16:00 Tracing watch argument parsing
5. 20:30 Adding the optional iteration argument
6. 27:00 Learning how multi-argument meta-commands parse
7. 31:00 Iteration defaults and preserving infinity
8. 39:30 Reviewing pg_stat_session counters and overhead