Re: problems with toast.* reloptions

On Wed, Aug 12, 2026 at 01:33:20PM -0500, Sami Imseih wrote:
> 1/ 0007 adds merge_toast_reloptions(), and for each option it calls
> find_reloption() to get the type and default. find_reloption() scans the
> entire relOpts[]. The options don't change, so it's just repeating the
> same work every time, which also includes strcmp to match the options by
> name.
>
> find_reloption() already runs initialize_reloptions(), so could
> initialize_reloptions() also build a small table of the options a toast
> table inherits from its main table. merge_toast_reloptions() then just
> iterates that table and no longer needs to call find_reloption() in the
> scan.
>
> This would help most when pg_stat_autovacuum_scores calls
> merge_toast_reloptions() for every toast table in its list, which occurs
> in 0008.

I considered this, but AFAICT that extra work actually pales in comparison
to the sequential scan of pg_class.

> 2/ There are three spots that repeat the work for a toast table,
> extractRelOptions() followed by a table_toast_map lookup and a
> merge_toast_reloptions(). For example, when do_autovacuum() performs the
> pass on the toast tables:
>
> [...]
>
> as well as table_recheck_autovac() and pg_stat_get_autovacuum_scores().
>
> The job here is to find the "effective" toast options, and it might be
> worthwhile to turn this into a single helper for clarity.

Done in v10.

--
nathan