Re: DBD::mysql Re: Why is selectrow_hashref complaining about a fetch without execute?

On 20/07/15 14:15, Tim Bunce wrote:
> On Mon, Jul 20, 2015 at 08:55:40AM +0100, Martin J. Evans wrote:
>> On 19/07/15 15:41, Tim Bunce wrote:
>>
>> Please also see the issue I reported in DBI back in 2012:
>>
>> https://rt.cpan.org/Ticket/Display.html?id=81911
>>
>> I had to add various workarounds and a warning to DBD::ODBC.
>
> Ah, thanks for the reminder Martin! I'll add a comment on that case.
>
> Any thoughts about the general principle of changing the XS execute to
> return the value of the DBIc_ROW_COUNT IV if the int returned by
> dbd_st_execute is > 0 and DBIc_ROW_COUNT > 0?
>
> Tim.
>

I think that would work for me - I'm happy to test it our here if you want to give it a go.

IIRC, when this was last discussed the problem is that some drivers might not set DBIc_ROW_COUNT so you can't just use DBIc_ROW_COUNT. In fact, I just checked, and DBD::ODBC does not seem to call DBIc_ROW_COUNT other than to set it to 0 in ODBC.xsi (which is code from DBI anyway). Does that sound right?

If a driver is supposed to set DBIc_ROW_COUNT I'd rather change the drivers I maintain to do that especially since in ODBC and 64bit SQLRowCount already returns a 64 bit value. Is there some docs on that or perhaps you could just tell me or point me at a driver that does it correctly.

I'm having a frustrating day so far so perhaps have lost the ability to read diffs and C but in your change at
https://github.com/perl5-dbi/dbi/commit/29f6b9b76e9c637be31cb80f1a262ff68b42ef43#diff-cb6af96fe009d6f8d9d682415e1ab755

"if retval>0 (checked above) " I don't see where the "checked above" bit is.

it looks like:

if (retval == 0)
   ..
else if (retval == -1)
   ..
else if (retval <= -2)
   ..
else
   new stuff here
   retval could still be negative just not -1 or -2

Also, maybe a little picky but the comment "and DBIc_ROW_COUNT>0" does not match the code.

If no DBDs use DBIc_ROW_COUNT then that warning you've put in will do nothing. I'd like to see a driver which does use DBIc_ROW_COUNT and if there are none I'm happy to change DBD::ODBC initially to a) test the diff you just applied and b) test the suggested fix.

Martin