Re: assertion failure at cost_memoize_rescan()

On Mon, 17 Jun 2024 at 10:23, Tomas Vondra
<tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
> Interesting. Seems like a bug due to the two places clamping the values
> inconsistently. It probably does not matter in other contexts because we
> don't subtract the values like this, but here it triggers the assert.
>
> I guess the simplest fix would be to clamp "calls" the same way before
> calculating hit_ratio. That makes the ">= 0" part of the assert somewhat
> pointless, though.

"calls" comes from the value passed as the final parameter in
create_memoize_path().

There's really only one call to that function and that's in get_memoize_path().

return (Path *) create_memoize_path(root,
innerrel,
inner_path,
param_exprs,
hash_operators,
extra->inner_unique,
binary_mode,
outer_path->rows);

It would be good to know what type of Path outer_path is. Normally
we'll clamp_row_est() on that field. I suspect we must have some Path
type that isn't doing that.

KaiGai-san, what type of Path is outer_path?

David

David