Re: Sequence Access Method WIP

From: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Sequence Access Method WIP
Date: 2013-11-26 11:28:33
Message-ID: 529485E1.6090402@vmware.com
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On 11/24/13 19:15, Simon Riggs wrote:
> On 18 November 2013 07:36, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> wrote:
>> On 14.11.2013 22:10, Simon Riggs wrote:
>>>
>>> Includes test extension which allows sequences without gaps - "gapless".
>>
>> I realize this is just for demonstration purposes, but it's worth noting
>> that it doesn't actually guarantee that when you use the sequence to
>> populate a column in the table, the column would not have gaps. Sequences
>> are not transactional, so rollbacks will still produce gaps. The
>> documentation is misleading on that point. Without a strong guarantee, it's
>> a pretty useless extension.
>
> True.
>
> If I fix that problem, I should change the name to "lockup" sequences,
> since only one transaction at a time could use the nextval.
>
> Should I change the documentation, or just bin the idea?

Just bin it. It would be useful if it could guarantee gaplessness, but I
don't see how to do that.

- Heikki

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