Re: Open Source tool to deploy/promote PostgreSQL DDL

On 07/11/2018 04:01 PM, Ron wrote:
> On 07/11/2018 04:10 PM, Christopher Browne wrote:
> [snip]
>> ITIL surely does NOT specify the use of database rollback scripts as
>> THE SPECIFIED MECHANISM for a backout procedure.
>>
>> In practice, we tend to take database snapshots using filesystem
>> tools, as that represents a backout procedure that will work regardless
>> of the complexity of an upgrade.
>>
>> It is quite possible for an upgrade script to not be reversible.
>>
>> After all, not all matrices are invertible; there are a surprisingly 
>> large
>> number of preconditions that are required for that in linear algebra.
>>
>> And in databases, not all upgrades may be reversed via rollback scripts.
> 
> Does "rollback script" truly mean undoing what you just did in a 
> transaction-like manner?
> 

Hard to say without knowing the system you are using, but I would guess 
no. I use Sqitch and it uses the term revert:

https://metacpan.org/pod/sqitchtutorial#Status,-Revert,-Log,-Repeat

which I think is more accurate. I find it very handy feature when in 
development mode. Write script --> deploy --> test, if fails --> revert, 
rewrite deploy script --> deploy and so on.

-- 
Adrian Klaver
adrian.klaver@aklaver.com