Re: pg_sequence catalog

On Thu, Sep 1, 2016 at 12:00 AM, Andres Freund <andres@anarazel.de> wrote:
> On 2016-08-31 14:23:41 -0400, Tom Lane wrote:
>> Andres Freund <andres@anarazel.de> writes:
>> > On 2016-08-31 13:59:48 -0400, Tom Lane wrote:
>> >> You are ignoring the performance costs associated with eating 100x more
>> >> shared buffer space than necessary.
>>
>> > I doubt that's measurable in any real-world scenario. You seldomly have
>> > hundreds of thousands of sequences that you all select from at a high
>> > rate.
>>
>> If there are only a few sequences in the database, cross-sequence
>> contention is not going to be a big issue anyway.
>
> Isn't that *precisely* when it's going to matter? If you have 5 active
> tables & sequences where the latter previously used independent locks,
> and they'd now be contending on a single lock.
>

I may be missing something here, but why would it contend on a lock,
as per locking scheme proposed by Alvaro, access to sequence object
will need a share lock on buffer page.


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com