[DB-SIG] definition of .rowcount

[Peter Eisentraut]

On tis, 2012-06-12 at 10:07 -0400, Michael Bayer wrote:
> So as many of you know, MySQL has actually two options for how
> rowcount can be reported.  It can report the number of rows "found",
> that is, matched by the WHERE criterion of an UPDATE or DELETE
> statement, or it can report the number of rows that were actually
> updated or deleted, and here we're talking about an UPDATE that may or
> may not have had a net change in row value.   The Python MySQL drivers
> tend to default to the latter.    Every other database/DBAPI I've
> worked with only offers the former.

Even if the value that is stored before and after an update is logically
the same, this could fire triggers, so the row is still "affected".
Also, some data types aren't comparable, so you can't always know this.
So I think the problem with the alternative behavior of MySQL is that it
isn't even generally definable, so it can't possibly be the correct
answer for a general interface.

There is also the question of how this definition for the UPDATE command
extends to other commands.  It probably doesn't, in a sensible way
(well, maybe for REPLACE/INSERT ON DUPLICATE KEY UPDATE, but then you
might get a second-level inconsistency between the regular UPDATE and
the UPDATE run as part of the INSERT).

I agree that the terms could be clarified, nevertheless.