Re: Improving EXPLAIN's display of SubPlan nodes

Aleksander Alekseev <aleksander(at)timescale(dot)com> writes:
> Although something like:

> ```
> + Filter: (ANY (base_tbl.a = $1) FROM SubPlan 1 (returns $1))
> + SubPlan 1 (returns $1)
> ```

> ... arguably doesn't give much more information to the user comparing
> to what we have now:

> ```
> - Filter: (SubPlan 1)
> - SubPlan 1
> ```

Yeah, I would probably not have thought to do this on my own; but
we had an actual user request for it. I think arguably the main
benefit is to confirm "yes, this is the sub-select you think it is".

The main thing that's still missing compared to what is in the plan
data structure is information about which Param is which. I think
we have the subplan output Params relatively well covered through
the expedient of listing them in the generated plan_name, but it's
still not apparent to me how we could shoehorn subplan input
Params into this (or whether it's worth doing).

regards, tom lane