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

[Jeffrey Horner]

On Tue, Feb 4, 2014 at 8:51 PM, NISHIYAMA Tomoaki <
tomoakin using staff.kanazawa-u.ac.jp> wrote:

> Hi Jeff,
>
> I think A or B is preferred.
> Cloning feature is of little benefit with large undesired feature.
> When cloning occurs, the transaction state becomes independent, and
> any change made at the other connection may not be visible to the other
> connection.
> Doing such thing in a hidden scene should be best avoided.
>
> In RPostgreSQL, I removed the connection cloning about 2 years ago, which
> perhaps inherited from RMySQL.
>
> http://code.google.com/p/rpostgresql/source/diff?spec=svn230&r=230&format=side&path=/trunk/RPostgreSQL/R/PostgreSQLSupport.R


Then that settles it. I will implement B: warn users when there are pending
result sets, but get rid of them and proceed.

Paul, to allay your concerns, this new change should align behavior of
RMySQL with the rest of DBI dependent packages.

Thank you both for taking time to comment.

Jeff

>
>
> Some of the most likely scenario why users do not collect all the data
> after dbSendQuery(),
> could that they aren't concerned on the results at all, as they have
> submitted some SET, INSERT, or UPDATE statements. (Although it is better
> to check for any error.)
> Making this as a error might make them some stress.
> Emitting error would benefit only at a time they try to read the discarded
> result set.
>
> D would perhaps make too much complication of the program with little
> benefit.
> (I really do not see any good reason to *silently* make
> clone of the connection even as an option.)
>
> Kind regards,
> Tomoaki
> --
> Tomoaki NISHIYAMA
>
> Advanced Science Research Center,
> Kanazawa University,
> 13-1 Takara-machi,
> Kanazawa, 920-0934, Japan
>
>
> On 2014/02/05, at 8:27, Paul Gilbert wrote:
>
> > 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
> >>
> >>      [[alternative HTML version deleted]]
> >>
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> >>
> >
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