On 18/9/2025 13:35, David Rowley wrote:
On Thu, 18 Sept 2025 at 19:55, Andrei Lepikhov <lepi...@gmail.com> wrote:
Imagine if we had a hook within the ExecProcNode. In that scenario, we
could create a trivial extension that would stop the query after, let's
say, 10 minutes of execution and display the current state. This would
give us more reliable data on estimation and the state of the plan tree.
I recall something along those lines existing once in the extension
world. Or maybe just from a previous employer. I don't recall many of
the details. Maybe something like a function you pass an SQL string
and if you cancelled the query it reported the EXPLAIN ANALYZE done so
far. I assume it must have done something like LOG it as it couldn't
have shown the EXPLAIN as query results on cancel.
It looks like a makeshift solution. By implementing a callback, we could
elevate 'interrupter' to a first-class feature, enabling us to monitor
the state of the entire query tree (it is especially cool in EXPLAIN
ANALYZE mode when we may be OK with a partial result).
What's more interesting if Robert's work on nodes' extensibility
successes, it enables modules to save planning decisions in the plan.
Thereby, the in-executor callback provides a means to kick off the query
planned with incorrect estimations (e.g., too many spilled tuples).
Perhaps we should start working on introducing this type of callback/ hook?
--
regards, Andrei Lepikhov
