I tried out the patch you posted over at [1]. For those wanting an easy way to test it, or test the buggy behaviour in master without this patch, you can simply kill -STOP the checkpointer, so that DROP DATABASE hangs in RequestCheckpoint() (or you could SIGSTOP any other backend so it hangs in the barrier thing instead), and then you can just press ^C like this:
postgres=# create database db2; CREATE DATABASE postgres=# drop database db2; ^CCancel request sent ERROR: canceling statement due to user request After that you get: $ psql db2 psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: FATAL: database "db2" is invalid DETAIL: Use DROP DATABASE to drop invalid databases I suppose it should be a HINT? +# FIXME: It'd be good to test the actual interruption path. But it's not +# immediately obvious how. I wonder if there is some way to incorporate something based on SIGSTOP signals into the test, but I don't know how to do it on Windows and maybe that's a bit weird anyway. For a non-OS-specific way to do it, I was wondering about having a test module function that has a wait loop that accepts ^C but deliberately ignores ProcSignalBarrier, and leaving that running in a background psql for a similar effect? Not sure why the test is under src/test/recovery. While a database exists in this state, we get periodic autovacuum noise, which I guess we should actually skip? I suppose someone might eventually wonder if autovacuum could complete the drop, but it seems a bit of a sudden weird leap in duties and might be confusing (perhaps it'd make more sense if 'invalid because creating' and 'invalid because dropping' were distinguished). 2023-05-09 15:24:10.860 NZST [523191] FATAL: database "db2" is invalid 2023-05-09 15:24:10.860 NZST [523191] DETAIL: Use DROP DATABASE to drop invalid databases 2023-05-09 15:25:10.883 NZST [523279] FATAL: database "db2" is invalid 2023-05-09 15:25:10.883 NZST [523279] DETAIL: Use DROP DATABASE to drop invalid databases 2023-05-09 15:26:10.899 NZST [523361] FATAL: database "db2" is invalid 2023-05-09 15:26:10.899 NZST [523361] DETAIL: Use DROP DATABASE to drop invalid databases 2023-05-09 15:27:10.919 NZST [523408] FATAL: database "db2" is invalid 2023-05-09 15:27:10.919 NZST [523408] DETAIL: Use DROP DATABASE to drop invalid databases 2023-05-09 15:28:10.938 NZST [523456] FATAL: database "db2" is invalid 2023-05-09 15:28:10.938 NZST [523456] DETAIL: Use DROP DATABASE to drop invalid databases [1] https://www.postgresql.org/message-id/20230509013255.fjrlpitnj3ltur76%40awork3.anarazel.de
