Re: Memory consumed by child SpecialJoinInfo in partitionwise join planning

On Wed, Feb 14, 2024 at 9:50 AM Andrei Lepikhov
<a(dot)lepikhov(at)postgrespro(dot)ru> wrote:
>
> On 30/1/2024 12:44, Ashutosh Bapat wrote:
> > Thanks Vignesh. PFA patches rebased on the latest HEAD. The patch
> > addressing Amit's comments is still a separate patch for him to
> > review.
> Thanks for this improvement. Working with partitions, I frequently see
> peaks of memory consumption during planning. So, maybe one more case can
> be resolved here.
> Patch 0001 looks good. I'm not sure about free_child_sjinfo_members. Do
> we really need it as a separate routine? It might be better to inline
> this code.

try_partitionwise_join() is already 200 lines long. A separate
function is better than adding more lines to try_partitionwise_join().
Also if someone wants to call build_child_join_sjinfo() outside
try_partitionwise_join() may find free_child_sjinfo_members() handy.

> Patch 0002 adds valuable comments, and I'm OK with that.
>
> Also, as I remember, some extensions, such as pg_hint_plan, call
> build_child_join_sjinfo. It is OK to break the interface with a major
> version. But what if they need child_sjinfo a bit longer and collect
> links to this structure? I don't think it is a real stopper, but it is
> worth additional analysis.

If these extensions call build_child_join_sjinfo() and do not call
free_child_sjinfo_members, they can keep their child sjinfo as long as
they want. I didn't understand your concern.

--
Best Wishes,
Ashutosh Bapat