Re: Surprising behaviour of \set AUTOCOMMIT ON

On Mon, Aug 8, 2016 at 11:17 AM, David G. Johnston
<david.g.johnston@gmail.com> wrote:
> On Mon, Aug 8, 2016 at 11:02 AM, Robert Haas <robertmhaas@gmail.com> 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.
>>
>> 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.
>>
>> Aborting the server-side transaction - with or without notice -
>> doesn't seem very reasonable.
>>
>
> Best of both worlds?
>
> IF (ON_ERROR_STOP == 1)
> THEN (treat this like any other error)
> ELSE (send COMMIT; to server)

No, that's not a good idea.  The purpose of ON_ERROR_STOP is something
else entirely, and we shouldn't reuse it for an unrelated purpose.

-- 
Robert Haas
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