INSERT ... SELECTs are not cancelled on session disconnect

[teskje]

What version of Materialize are you using?

main

How did you install Materialize?

Built from source

What is the issue?

When one performs an INSERT ... SELECT statement with a long-running SELECT query, and then disconnects the session, adapter does not cancel the in-progress peek.

To reproduce (courtesy of @philip-stoev):

1. Start a long-running INSERT ... SELECT, e.g.:

   CREATE TABLE t1 (f1 INTEGER);
   INSERT INTO t1 WITH MUTUALLY RECURSIVE flip(x INTEGER) AS (VALUES(1) EXCEPT ALL SELECT * FROM flip) SELECT * FROM flip;

   Note that this example uses WMR, which needs to be enable through --unsafe-mode or the feature flag, to produce a divergent query that will never return. Any other slow query works too.

2. Forcefully disconnect the session from another terminal, e.g.:

   $ killall psql
   

Observe that adapter is not immediately cancelling the in-progress peek with the compute controller. The cancellation only happens when the statement timeout occurs. This behavior is different than for regular SELECT queries, which are cancelled immediately on session disconnect.

Note that the bug might be difficult to observe, depending on your test query. For example, the above divergent WMR query will never stop running regardless of whether the peek was cancelled or not (#16800). I suggest you instrument the code to print when the compute controller receives a CancelPeeks command.

Relevant log output

No response