By default, psql will fetch the entire result first then print it out. This is usually fine until you need to fetch more rows than your client's RAM. To fix that, you can run "\set FETCH_COUNT 10000". Then psql will use a cursor which only fetches 10000 rows at a time, using a constant amount of RAM.

This can be handy if e.g. you typically run psql on the server/container running postgres itself and you want to avoid an accidentally large query from oomkilling your database. You can set FETCH_COUNT per database and per user with ALTER: https://www.postgresql.org/docs/current/config-setting.html#...