Subject: Re: upgrade path from PG 8.3 to PG 9.5
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From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
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Date: Wed, 22 Mar 2017 09:09:15 +0200
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On 21/03/2017 21:00, Scott Marlowe wrote:
> On Tue, Mar 21, 2017 at 10:54 AM, Stephen Frost <sfrost@snowman.net> wrote:
>> Greetings,
>>
>> * David G. Johnston (david.g.johnston@gmail.com) wrote:
>>> On Tue, Mar 21, 2017 at 9:40 AM, Stephen Frost <sfrost@snowman.net> wrote:
>>>> * Thorsten Schöning (tschoening@am-soft.de) wrote:
>>>>> Guten Tag Keith,
>>>>> am Donnerstag, 23. Februar 2017 um 18:57 schrieben Sie:
>>>>>
>>>>>> You can go directly from 8.3 to 9.5. Just be sure and use the
>>>>>> pg_dump from 9.5 to generate the dump file from 8.3.
>>>>> Is there a specific reason for that? My current approach for upgrades
>>>>> was dumping the old database using the old pg_dump, uninstalling the
>>>>> old Postgres, installing the new one and restore from the old dump.
>>>> Yes.  Using the older pg_dump may result in dumps that can't be restored
>>>> into the newer version of PG because things like keywords have been
>>>> added and must now be quoted.  There are possibly other things that have
>>>> been changed between the old version and the new one which would also
>>>> require the new pg_dump to be used, but keywords are the big one.
>>> The proper solution to the keyword/identifier quoting problem is to use
>>> "--quote-all-identifiers".
>> Using the version of pg_dump to which you are upgrading is an entirely
>> supported and 'proper' approach to dealing with that issue.  Using
>> --quote-all-identifiers, in my opinion anyway, leads to rather ugly
>> results.
>>
>> As I also mention, there are other things in newer versions that pg_dump
>> does its best to address (including things like checking for role names
>> in older versions starting with "pg_", which is not allowed in 9.6+).
>> Using the pg_dump from the version of PG to which you are upgrading is
>> the correct and supported approach to doing upgrades.  Using
>> --quote-all-identifiers is not.
> Yeah there are plenty of little road bumps to hit especially when
> going from something  as old as 8.3 to 9.5. emcoding issues pop up etc
> etc.
>
> Using the new version to dump is THE way to go if you are gonna dump restore.
>
> IF you need the minimal amount of downtime possible, the only
> reasonable solution is some form of logical replication like slony or
> longdiste etc.
We used pg_upgrade recently for migrating from 8.3 -> 9.4 (the last version which supports 8.3), and it went nice. We had some custom functions in C, and pg_upgrade is a disciplined way to deal with 
the migration.
We will deploy this migration procedure to over 100 servers running 8.3.
> According to this page: http://slony.info/documentation/requirements.html
>
> slony 2.2.5 supports versions from 8.3 to 9.5 so you can upgrade from
> one to the other in one fell swoop and your downtime will be measured
> in seconds, or minutes at most. I suggest create a pair of test
> servers running 8.3 and 9.5 to test the migration on ahead of time.
> If you don't need to keep downtime to a minimum dump/restore is WAY
> easier and you can do a test run while the main server is running just
> by taking a backup and see if it restores cleanly and properly to the
> new 9.5 machine. If you do want minimal downtime, learning slony or
> some other logical replication system is worth your time. Slony docs
> have a fairly old but still mostly accurate how to page here:
> http://slony.info/documentation/1.2/versionupgrade.html
>


-- 
Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt


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