Re: [PATCH] Optionally record Plan IDs to track plan changes for a query

On Thu, 2 Jan 2025 12:46:04 -0800
Lukas Fittl <lukas(at)fittl(dot)com> wrote:

> this proposed patch set adds:
>
> 1. An updated in-core facility to optionally track Plan IDs based on
> hashing the plan nodes during the existing treewalk in setrefs.c -
> controlled by the new "compute_plan_id" GUC
> 2. An example user of plan IDs with a new pg_stat_plans extension in
> contrib, that also records the first plan text with EXPLAIN (COSTS
> OFF)
>
> My overall perspective is that (1) is best done in-core to keep
> overhead low, whilst (2) could be done outside of core (or merged
> with a future pg_stat_statements) and is included here mainly for
> illustration purposes.

And 2025 is starting with a bang! Nice to see this email! Being able to
collect telemetry that indicates when plan changes happened would be
very useful.

The specifics of how a plan ID is generated are going to have some edge
cases (as you noted)

I concur that the ideal place for this to eventually land would be
alongside queryid in pg_stat_activity

-Jeremy