From: Elliot Chance <elliotchance@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-admin@postgresql.org
Subject: Re: pg_dump and XID limit
Date: Wed, 24 Nov 2010 20:59:59 +1100
Message-ID: <C7D1CBBF-B65F-4047-B9BC-933D9C02D502@gmail.com> (raw)
In-Reply-To: <6420.1290578869@sss.pgh.pa.us>
References: <DC1E3319-08CD-4C61-9565-06D744260261@gmail.com>
<6420.1290578869@sss.pgh.pa.us>
On 24/11/2010, at 5:07 PM, Tom Lane wrote:
> Elliot Chance <elliotchance@gmail.com> writes:
>> This is a hypothetical problem but not an impossible situation. Just curious about what would happen.
>
>> Lets say you have an OLTP server that keeps very busy on a large database. In this large database you have one or more tables on super fast storage like a fusion IO card which is handling (for the sake of argument) 1 million transactions per second.
>
>> Even though only one or a few tables are using almost all of the IO, pg_dump has to export a consistent snapshot of all the tables to somewhere else every 24 hours. But because it's such a large dataset (or perhaps just network congestion) the daily backup takes 2 hours.
>
>> Heres the question, during that 2 hours more than 4 billion transactions could of occurred - so what's going to happen to your backup and/or database?
>
> The DB will shut down to prevent wraparound once it gets 2 billion XIDs
> in front of the oldest open snaphot.
>
> regards, tom lane
Wouldn't that mean at some point it would be advisable to be using 64bit transaction IDs? Or would that change too much of the codebase?
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To: pgsql-admin@postgresql.org
Cc: elliotchance@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: pg_dump and XID limit
In-Reply-To: <C7D1CBBF-B65F-4047-B9BC-933D9C02D502@gmail.com>
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