[R-sig-DB] RFI on changing behavior in next RMySQL release

[Paul Gilbert]

Jeff

The one thing I would be concerned about is if the (default) behaviour 
of dbGetQuery() in RMySQL deviates much from dbGetQuery() in other DBI 
packages like TSPostgreSQL, TSSQLite, ... . I am using code that is 
generic across all these.

 From your description I am not sure if this problem is really specific 
to RMySQL, or also happens with other engines, so, whether your proposed 
change will make things more similar or less similar. (I have not been 
using dbSendQuery() so may have just been luck.)

Paul

On 02/03/2014 11:46 AM, Jeffrey Horner wrote:
> Hi,
>
> A situation has been brought to my attention by two RMySQL users who have
> posted their issues on github.
>
> As followers of this mailing list, most will be familiar with the two ways
> in which SQL queries are executed and results obtained via the DBI:
>
> 1. users execute dbSendQuery(), get back a result set object and use
> subsequent functions dbHasCompleted(), fetch(), and possibly
> dbClearResult() act on the result set.
>
> 2. users execute dbGetQuery() to perform just one function to execute the
> SQL, gather the result set, and return to the user.
>
> In RMySQL, connection level options can be set that affect the work done
> for the duration of the connection only. For instance, one user sets the
> connection level character set to ensure that all results are transferred
> in UTF8.
>
> The issue is that RMySQL will create temporary connections unbeknownst to
> the user during a call to dbGetQuery() if the user has previously performed
> a dbSendQuery() without getting rid of the returned result set object. In
> essence, this is a user who has not been enlightened on exactly what's
> going on, they didn't fully read and comprehend the documentation.
>
> I'd like to get rid of the temporary connection feature, let's call it
> cloning the connection as that's the name of the low level mysql C function
> that takes care of creating the temporary connection, but I'd like to make
> this change in a way that doesn't place too much stress on the user.
>
> So, here are some options I've come up with to alter dbGetQuery() and the
> other functions that create temporary connections, but I'd like to get the
> list users opinions on this before I release:
>
> A) Do I silently remove the pending result set objects altogether,
> B) Do I do A but with a warning,
> C) Do I throw an error and let the user fix his/her code,
> D) Do I add a dbConnect() connection argument called 'clone' that tells
> whether or not to allow temporary cloning of the connection, and what
> should the default argument value be, TRUE or FALSE?
>
> D) was suggested by a github user, so I'm inclined to go with that.
>
> Thanks for your thoughts on this.
>
> Jeff
>
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