Re: Rename a column if not already renamed.?

On 8/21/19 7:52 AM, Day, David wrote:
> I agree the function could be improved to deal with both old and new name existing simultaneously.
> That is almost certainly the root cause, and one that I would confirm if the tester and site were currently available to me.
>
> Our work flow for this scenario is something like:
>
> 1. 9.6 pg_dump takes a snapshot of our 9.6 database.
> 2. Postgres is upgraded/freshly installed to 11.3..
> 3. The 9.6 database is restored using the version 11 pg_restore tool.

In 3) you are restoring to the new 11.3 instance, correct?

>
> 4. Once our application process starts up, it sees there is a patch available in it's old branch that is one greater then it's restored 9.6 content.
> That happens to be a merge patch which resets the expectations.
> It attempts to apply all patches in the new branch since the point of divergence and runs into my current issue.
>
> It occurs to me I could simply put an exception handler in the rename column function and I would likely proceed merrily along.
> But curiosity is killing me and the cat. What is causing the old name to persist in the pg_attribute table after the rename. ?

If you are indeed working on the new instance pg_attribute would have no
'memory' of the dropped column. It would seem to me to come down to
what is passed into sys.rename_column() as old_name_, new_name.

>
> Would a stale function referencing the old column name be a contributor?
>
>
> Regards
>
>
> Dave Day
>
>
>
>
> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Tuesday, August 20, 2019 4:57 PM
> To: Day, David <david(dot)day(at)redcom(dot)com>
> Cc: Luca Ferrari <fluca1978(at)gmail(dot)com>; pgsql-general(at)postgresql(dot)org
> Subject: Re: Rename a column if not already renamed.?
>
> "Day, David" <david(dot)day(at)redcom(dot)com> writes:
>> The error is something like column already exists and
>
> Not sure about the workflow this function is used within, but maybe you need to consider what to do when both the old and new column names exist.
> Because that sure sounds like what is happening.
>
> regards, tom lane
>
>
>
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com