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From: Heikki Linnakangas <[email protected]>
To: Ashutosh Bapat <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: [email protected] <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Rahila Syed <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Subject: Re: Shared hash table allocations
Date: Sat, 4 Apr 2026 02:58:42 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On 03/04/2026 20:32, Heikki Linnakangas wrote:
> On 03/04/2026 16:03, Ashutosh Bapat wrote:
>> On Thu, Apr 2, 2026 at 10:15 PM Heikki Linnakangas <[email protected]> 
>> 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!

And committed the rest of the patches from this thread now too, after 
some small fixes and cleanups. Thanks again!

- Heikki

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