Restoring into 11.3 instance the 9.6 dump  ? ->  yes.

For the upgrade scenario, I  confirmed that both old column name and new name 
are in the pg_attribute table at the time the patch attempts to rename it.
Why both  is a big question.
However,
It is easy enough to re-write the column rename function to deal with the 
simultaneous possibility.  I will include the redefined function in the merge 
patch and see how it goes.

I'll update the thread after some further exploration.

Thanks all for your assistance.


-----Original Message-----
From: Adrian Klaver [mailto:adrian.kla...@aklaver.com] 
Sent: Wednesday, August 21, 2019 11:47 AM
To: Day, David <david....@redcom.com>; Tom Lane <t...@sss.pgh.pa.us>
Cc: Luca Ferrari <fluca1...@gmail.com>; pgsql-gene...@postgresql.org
Subject: 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:t...@sss.pgh.pa.us]
> Sent: Tuesday, August 20, 2019 4:57 PM
> To: Day, David <david....@redcom.com>
> Cc: Luca Ferrari <fluca1...@gmail.com>; pgsql-gene...@postgresql.org
> Subject: Re: Rename a column if not already renamed.?
> 
> "Day, David" <david....@redcom.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.kla...@aklaver.com

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