Re: [PATCH] pgstat: Add helper to drop entries from a stats kind's hash

On Thu, Oct 29, 2026 at 11:30:45AM -0500, Sami Imseih wrote:
> I kept the kind check in the loop because, when kind maps to the shared
> hash, scanning that hash also visits entries for other kinds. Without
> the check, a kind-specific scan could consider those entries too,
> including in the NULL do_drop path.

Okay. Looks globally fine.

> The added tests cover both cases: the callback path verifies
> that entries of another kind are not passed to the callback, and the NULL
> do_drop path verifies that dropping all entries of the custom stats kind
> does not drop a relation stats entry in the same shared hash.

- for (int h = 0; h < pgStatLocal.num_var_hashes; h++)
+ if (filter_by_kind)
{
+ Assert(kind >= PGSTAT_KIND_MIN && kind <= PGSTAT_KIND_MAX);
+ Assert(pgStatLocal.kind_hash[kind] != NULL);
+ }
+
+ for (int h = 0; h < num_hashes; h++)
+ {
+ dshash_table *hash = filter_by_kind ?
+ pgStatLocal.kind_hash[kind] : pgStatLocal.var_hashes[h];

Instead of allocating the dshash_table pointer in the loop, perhaps
use temporary variables to store the number of hashtables and an array
of them. That would matter if somebody would like to extend this API
to a subset of N hashtables, where 1 < N < num_var_hashes?
--
Michael