From: | Rob Sargent <robjsargent(at)gmail(dot)com> |
---|---|
To: | "Peter J(dot) Holzer" <hjp-pgsql(at)hjp(dot)at> |
Cc: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: Could postgres12 support millions of sequences? (like 10 million) |
Date: | 2020-03-20 23:11:42 |
Message-ID: | 0D8F2D62-C0E4-4D6C-B77C-9A2FEB78898C@gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
> On Mar 20, 2020, at 4:59 PM, Peter J. Holzer <hjp-pgsql(at)hjp(dot)at> wrote:
>
> On 2020-03-19 16:48:19 -0700, David G. Johnston wrote:
>> First, it sounds like you care about there being no gaps in the records you end
>> up saving. If that is the case then sequences will not work for you.
>
> I think (but I would love to be proven wrong), that *nothing* will work
> reliably, if
>
> 1) you need gapless numbers which are strictly allocated in sequence
> 2) you have transactions
> 3) you don't want to block
>
> Rationale:
>
> Regardless of how you get the next number, the following scenario is
> always possible:
>
> Session1: get next number
> Session2: get next nummber
> Session1: rollback
> Session2: commit
>
> At this point you have a gap.
>
> If you can afford to block, I think a simple approach like
>
> create table s(id int, counter int);
> ...
> begin;
> ...
> update s set counter = counter + 1 where id = $whatever returning counter;
> -- use counter
> commit;
>
> should work. But that effectively serializes your transactions and may
> cause some to be aborted to prevent deadlocks.
>
> hp
OP has said small gaps are ok. To me that says the requirement is capricious but we haven’t heard the rationale for the requirement yet (or I missed it)
Aside: apologies for the empty message earlier
From | Date | Subject | |
---|---|---|---|
Next Message | Peter J. Holzer | 2020-03-20 23:29:29 | Re: Could postgres12 support millions of sequences? (like 10 million) |
Previous Message | Peter J. Holzer | 2020-03-20 22:58:42 | Re: Could postgres12 support millions of sequences? (like 10 million) |