Unlimited memory consumption with long-lived connection

If I execute the attached python script against a postgresql 15.2 (Ubuntu
15.2-1.pgdg22.10+1) server, with the default configuration (eg shared_buffers =
128M), then the server memory usage goes up and up, apparently endlessly. After
about 10 minutes (on my laptop) pg_top shows RES memory usage for the back-end
handling the connection as greater than 1 gigabyte, which seems far too high
given the server configuration. The script just performs the same SELECT
endlessly in a loop. The memory is released when the script is killed.

Platform: Ubuntu 22.10; Linux version 5.19.0-31-generic; x86-64.

PS: The testcase was reduced from a script that kept a connection open for a
long time in order to LISTEN, and would execute a query using the same
connection every time there was a notification on the channel. It consumed ever
more memory to the point of crashing the postgresql server. Changing the script
to perform the query using a new short-lived connection was an effective workaround.