Re: Huge memory consumption on partitioned table with FKs

On 2020-Nov-26, Kyotaro Horiguchi wrote:

> This shares RI_ConstraintInfo cache by constraints that shares the
> same parent constraints. But you forgot that the cache contains some
> members that can differ among partitions.
> 
> Consider the case of attaching a partition that have experienced a
> column deletion.

I think this can be solved easily in the patch, by having
ri_BuildQueryKey() compare the parent's fk_attnums to the parent; if
they are equal then use the parent's constaint_id, otherwise use the
child constraint.  That way, the cache entry is reused in the common
case where they are identical.

I would embed all this knowledge in ri_BuildQueryKey though, without
adding the new function ri_GetParentConstOid.  I don't think that
function meaningful abstraction value, and instead it would make what I
suggest more difficult.