Re: Surprising behaviour of \set AUTOCOMMIT ON

On 08/08/16 17:02, Robert Haas wrote:
> On Mon, Aug 8, 2016 at 10:10 AM, Rahila Syed <rahilasyed90@gmail.com> wrote:
>> Thank you for inputs everyone.
>>
>> The opinions on this thread can be classified into following
>> 1. Commit
>> 2. Rollback
>> 3. Error
>> 4. Warning
>>
>> As per opinion upthread, issuing implicit commit immediately after switching
>> autocommit to ON, can be unsafe if it was not desired.  While I agree that
>> its difficult to judge users intention here, but if we were to base it on
>> some assumption, the closest would be implicit COMMIT in my opinion.There is
>> higher likelihood of a user being happy with issuing a commit when setting
>> autocommit ON than a transaction being rolled back.  Also there are quite
>> some interfaces which provide this.
>>
>> As mentioned upthread, issuing a warning on switching back to autocommit
>> will not be effective inside a script. It won't allow subsequent commands to
>> be committed as set autocommit to ON is not committed. Scripts will have to
>> be rerun with changes which will impact user friendliness.
>>
>> While I agree that issuing an ERROR and rolling back the transaction ranks
>> higher in safe behaviour, it is not as common (according to instances stated
>> upthread) as immediately committing any open transaction when switching back
>> to autocommit.
> 
> I think I like the option of having psql issue an error.  On the
> server side, the transaction would still be open, but the user would
> receive a psql error message and the autocommit setting would not be
> changed.  So the user could type COMMIT or ROLLBACK manually and then
> retry changing the value of the setting.

This is my preferred action.

> Alternatively, I also think it would be sensible to issue an immediate
> COMMIT when the autocommit setting is changed from off to on.  That
> was my first reaction.

I don't care for this very much.

> Aborting the server-side transaction - with or without notice -
> doesn't seem very reasonable.

Agreed.
-- 
Vik Fearing                                          +33 6 46 75 15 36
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support