Re: RFC: [b]lob_read in DBD::ODBC and other DBD differences

Tim Bunce wrote:
> On Tue, Jul 20, 2010 at 09:46:42PM +0100, Martin J. Evans wrote:
>> [...]
>>
>> As a result of the above, I don't see any way of supporting the existing
>> blob_read in DBI and as it is undocumented anyway and no DBDs seem to
>> use it
> 
> Feel free to mark it deprecated in the DBI docs..

It turns out I was mistaken as DBD::Oracle does implement blob read
although I've not tested it works. Someone, in the distant past
attempted an implementation in DBD::ODBC but it does not work and is
seriously flawed.

I guess since DBD::Oracle does implement it I should document it?

I have implemented my own odbc_lob_read and if I can find time I might
try and wrap a blob_read around it.

>> I've put a test implementation together as:
>>
>> odbc_lob_read(sth, colno, buf, length, \%attrs)
>>
>> where \%attrs can contain TYPE => SQL_type.
> 
>> I appreciate this RFC is quite long and I'm guessing few people will get
>> to the end. Increasingly, I'm working with several DBDs and the
>> differences between them (beyond SQL differences) is proving VERY
>> frustrating. It would be nice to try and sort out lob reading and whilst
>> I'm on a roll, SQLMoreResults/more_results, last_insert_id, lob_write,
>> binding with a specific type etc  but I guess since some of these have
>> been covered before and we didn't get too far in the past that perhaps
>> there is not a lot of interest in it. I'd like to fit DBD::ODBC with
>> DBI's blob_read but I don't think it works for DBD::ODBC as it stands
>> and I note other DBDs have provided their own lob reading methods
>> substantially different so I'm guessing they found that too.
> 
> I encourage driver authors to implement a 'natural' private API first
> before working together to agree on a common API for the DBI.
> (The blob_read API is an example of what happens when the DBI specifies
> things before drivers support them.)

Yes although I slightly misinformed you - sorry. I'll try and revisit
this in the next few weeks.

>> With Perl 6 perhaps on the horizon and Tim's current interest in JDBC I
>> think we are well advised to sort some of this out in Perl 5 first. It
>> makes little difference to me right now as I'll implement what I need
>> now and move on but I'm prepared to work to a DBI interface for the
>> common goal. Some of this is not going to go away - you only have to
>> watch perl monks to see the frustration with last_insert_id, lob
>> reading, binding columns with types etc across DBDs to know this is
>> proving troublesome for the average user.
> 
> Tim.

Martin
-- 
Martin J. Evans
Easysoft Limited
http://www.easysoft.com