Re: version upgrade

On 9/1/2004 1:51 PM, Serguei A. Mokhov wrote:

> Date: Tue, 31 Aug 2004 23:35:18 -0400
>
> On 8/31/2004 9:38 PM, Andrew Rawnsley wrote:
>
>> On Aug 31, 2004, at 6:23 PM, Marc G. Fournier wrote:
>>
>>> On Tue, 31 Aug 2004, Josh Berkus wrote:
>>>
>>>> Andrew,
>>>>
>>>>> If I were loony enough to want to make an attempt at a version
>>>>> updater
>>>>> (i.e. migrate a
>>>>> 7.4 database to 8.0 without an initdb), any suggestions on where to
>>>>> poke first? Does a
>>>>> catalog/list of system catalog changes exist anywhere? Any really
>>>>> gross
>>>>> problems immediately
>>>>> present themselves? Is dusting off pg_upgrade a good place to start,
>>>>> or
>>>>> is that a dead end?
>>>>
>>>> Join the Slony project? Seriously, this is one of the uses of
>>>> slony. All
>>>> you'd need would be a script that would:
>>>>
>>
>> I thought of this quite a bit when I was working over eRServer a while
>> back.
>>
>> Its _better_ than a dump and restore, since you can keep the master up
>> while the
>> 'upgrade' is happening. But Mark is right - it can be quite
>> problematic from an equivalent
>> resource point of view. An in-place system (even a faux setup like
>> pg_upgrade) would be
>> easier to deal with in many situations.
>
> | There is something that you will not (or only under severe risk) get
> | with an in-place upgrade system. The ability to downgrade back in the
> | case, your QA missed a few gotchas. The application might not instantly
> | eat the data, but it might start to sputter and hobble here and there.
> |
> | With the Slony system, you not only switch over to the new version. But
> | you keep the old system as a slave. That means that if you discover 4
> | hours after the upgrade that the new version bails out with errors on a
> | lot of queries from the application, you have the chance to switch back
> | to the old version and have lost no single committed transaction.
>
> Just asking: how far back in time Slony can "downgrade" or keep the older
> servers in "slavery"? 6.5? I haven't tried it yet, hence, the question.
>

Slony runs on 7.3.3 and better.

Jan

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