On Tue, Jul 7, 2026 at 2:31 PM Richard Guo <[email protected]> wrote: > Attached is v2 addressing this. For a single grouping key, at most > one NULL group remains, so we set it to 1 / (ndistinct + 1). With > multiple grouping keys, the surviving NULL count is underdetermined, > so we approximate it as zero; NULLs collapse far more aggressively > than non-NULLs, so the real fraction is well below the base table's, > and erring low keeps estimates on the hash-join-favoring side.
I've pushed the v2 patch. - Richard
