Re: Add memory/disk usage for WindowAgg nodes in EXPLAIN

On Thu, 19 Sept 2024 at 12:01, Tatsuo Ishii <ishii(at)postgresql(dot)org> wrote:
> > Could you add the two sizes together and take the storage type from
> > the tuplestore with the highest storage size?
>
> I don't think this works because tuplestore_begin/tuplestore_end are
> called while executing the node (ExecRecursiveUnion).
>
> I think the way you are proposing only shows the stats last time when
> those tuplestore are created.

That code could be modified to swap the tuplestores and do a
tuplestore_clear() instead of tuplestore_end() followed by
tuplestore_begin_heap().

It's likely worthwhile from a performance point of view. Here's a
small test as an example:

master:
postgres=# with recursive cte (a) as (select 1 union all select
cte.a+1 from cte where cte.a+1 <= 1000000) select count(*) from cte;
Time: 219.023 ms
Time: 218.828 ms
Time: 219.093 ms

with attached patched:
postgres=# with recursive cte (a) as (select 1 union all select
cte.a+1 from cte where cte.a+1 <= 1000000) select count(*) from cte;
Time: 169.734 ms
Time: 164.841 ms
Time: 169.168 ms

David