Re: Shared hash table allocations

On 03/04/2026 16:03, Ashutosh Bapat wrote:
> On Thu, Apr 2, 2026 at 10:15 PM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>>> I think the release notes should "nudge" all the
>>> users who use non-default max_locks_per_transaction to increase it if
>>> they see "out of memory" errors. I don't think it should provide a
>>> blanket advise to double their locks
>>
>> How about:
>>
>> "If you had previously set max_locks_per_transaction, you might need to
>> set it to a higher value in v19 to avoid "out of shared memory" errors.
>> If you are unsure what to set it to and don't mind the increased memory
>> usage, you can double the value to ensure that you can acquire at least
>> as many locks as before"
>
> The wiggle room is 100KB fixed + 10% of other two structures, so value
> by which it should be increased is partly fixed and partly a multiple
> of current value. "double the value" is simplest advice we can give.
> +1.

Ok, committed these patches to remove the safety margins, make LOCK and
PROCLOCK fixed-size, and change the default to
max_locks_per_transaction=128. I will do one final self-review of the
remaining earlier patches from this thread next; I believe they're ready
to be committed too.

Thanks for the review!

- Heikki