[R-sig-DB] Add a "dbSendUpdate" function to DBI?

[Paul Gilbert]

On 09/04/2014 10:53 AM, Hadley Wickham wrote:
> The problem with that approach is that you end up with a lot of code like:
>
> if (!dbBegin(con))  stop(dbGetException())
> ...
> if (!dbExecute(con, sql)) stop(dbGetException())
> ...
> if (!dbCommit(con))  stop(dbGetException())
>
> where the developer is responsible for always checking that the
> operation succeeded. If you throw an error, then the code is simpler:
>
> dbBegin(con)
> ...
> dbExecute(con, sql)
> ...
> dbCommit(con)
>

I think this depends on the code. There are frequently situations where 
it is nice to have a function that is certain to return a logical value, 
so not have to catch exceptions and parse for all possibilities. (BTW, 
if error message text is to be returned then that can be set as an 
attribute to the logical value.) My feeling is it would be nice to have 
both, one function certain to return a logical, and one that will throw 
an error. If one is a simple wrapper to the other then only one method 
needs to be implemented and the DBI default can look after the other.

Paul

> Given that we're using a language with exceptions, it seems better to
> use them, rather than adopting the standard C error handling
> mechanism.
>
> Hadley
>
> On Thu, Sep 4, 2014 at 9:45 AM, Peter Meißner
> <peter.meissner using uni-konstanz.de> wrote:
>> IMHO
>>
>> the general approach should be:
>>
>> - as long as R does deliver the the queries to the DB and the DB does give
>> response there should never ever be an R error - the function did what it
>> should do: making sure things were delivered to DB
>>
>> - the return than should depend on what the DB said:
>>    * 0/TRUE                    - no error, nothing else to say
>>    * 1/FALSE                   - DB does complain somehow
>>    * text/whatever appropriate - something was returned, ...
>>
>> - if however connection was lost during the execution of the function so it
>> cannot be sure delivery went as expected an error should be issued
>>
>> Best, Peter
>>
>>
>>
>> Am 04.09.2014 16:28, schrieb Denis Mukhin:
>>
>>> In ROracle we standardized on the second approach, namely always return
>>> TRUE, otherwise throw an error.
>>>
>>> Also since UPDATE is not the only operation that does not return any
>>> results (although it might with a RETURNING clause) would a more generic
>>> name be more appropriate here? Besides DMLs there are also DDLs. Something
>>> like dbExecute(), dbSubmit(), dbSend() ...
>>>
>>> Denis
>>>
>>> -----Original Message-----
>>> From: Hadley Wickham [mailto:hadley using rstudio.com]
>>> Sent: Thursday, September 04, 2014 9:13 AM
>>> To: MacQueen, Don
>>> Cc: Simon Urbanek; R-sig-DB using r-project.org
>>> Subject: Re: [R-sig-DB] Add a "dbSendUpdate" function to DBI?
>>>
>>> A thought: should dbSendUpdate() return a boolean indicating success, or
>>> always return TRUE, otherwise throwing an error?
>>>
>>> Hadley
>>>
>>> On Wed, Sep 3, 2014 at 3:59 PM, MacQueen, Don <macqueen1 using llnl.gov> wrote:
>>>>
>>>> Hadley,
>>>>
>>>> Since you mentioned DBI 0.3 in a recent email, could I make a request
>>>> to add a dbSendUpdate() function to DBI, like the one in RJDBC?
>>>>
>>>> require(RJDBC)
>>>>
>>>>> find('dbSendQuery')
>>>>
>>>> [1] "package:RJDBC" "package:DBI"
>>>>
>>>>> find('dbSendUpdate')
>>>>
>>>> [1] "package:RJDBC"
>>>>
>>>> And from ?dbSendUpdate
>>>>
>>>>     'dbSendQuery' and 'dbSendUpdate' submit a SQL query to the
>>>>     database. The difference between the two is only that
>>>>     'dbSendUpdate' is used with DBML queries and thus doesn't return
>>>>     any result set.
>>>>
>>>> I would find this helpful, because I could then use scripts unmodified
>>>> with either ROracle or RJDBC.
>>>> (I suppose adding it to DBI would mean that the one in RJDBC would
>>>> have to be modified.)
>>>>
>>>>
>>>> I have:
>>>>
>>>> Package Version
>>>>     "DBI" "0.3.0"
>>>>
>>>> Package Version
>>>> "RJDBC" "0.2-4"
>>>>
>>>>
>>>> Thanks
>>>> -Don
>>>>
>>>> --
>>>> Don MacQueen
>>>> Lawrence Livermore National Laboratory
>>>> 7000 East Ave., L-627
>>>> Livermore, CA 94550
>>>> 925-423-1062
>>>>
>>>
>>>
>>>
>>> --
>>> http://had.co.nz/
>>>
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>>>
>>
>> --
>> Peter Meißner
>> Workgroup 'Comparative Parliamentary Politics'
>> Department of Politics and Administration
>> University of Konstanz
>> Box 216
>> 78457 Konstanz
>> Germany
>>
>> +49 7531 88 5665
>> http://www.polver.uni-konstanz.de/sieberer/home/
>>
>>
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