Re: BUG #19836: Backend crash with large hash partition modulus

On Sun, 8 Nov 2026 at 04:54, PG Bug reporting form
<noreply(at)postgresql(dot)org> wrote:
> The following SQL crashes PostgreSQL 20devel (72b9498df9a, macOS ARM64):
> CREATE TABLE parent (i integer) PARTITION BY HASH (i);
> CREATE TABLE p0 PARTITION OF parent
> FOR VALUES WITH (MODULUS 3, REMAINDER 0);
> CREATE TABLE p1 PARTITION OF parent
> FOR VALUES WITH (MODULUS 2147483646, REMAINDER 2);

Thanks for the report.

It seems fine to just do:

@@ -2919,8 +2919,8 @@ check_new_partition_bound(char *relname, Relation parent,

if (partdesc->nparts > 0)
{
- int
greatest_modulus;
- int remainder;
+ int64 greatest_modulus;
+ int64 remainder;

That'll prevent the wrap and allow the do/while loop to terminate when
remainder is >= greatest_modulus. Bumping greatest_modulus isn't
really required, but I did that because I thought it was neater to
keep them the same size.

I can patch this when the freeze is over.

David