[Dbix-class] Issue with DBIx::Class::ResultSet::find_or_create():

[Matt S Trout]

On Sat, Jul 28, 2007 at 09:30:20AM -0400, Christopher H. Laco wrote:
> Matt S Trout wrote:
> > On Fri, Jul 27, 2007 at 06:38:19PM -0700, Mesdaq, Ali wrote:
> >> This came up in the Catalyst list today so I am posting here for
> >> discussion or bug reporting.
> >>
> >> The issue is that it seems the find_or_create() call can have a hiccup
> >> in high load situations where find_or_create is called more than once at
> >> the same time with the same value. So what happens is both calls try to
> >> do a find and return nothing then they attempt to insert and once
> >> succeeds and one gets an error of:
> >>
> >> DBIx::Class::ResultSet::find_or_create(): DBI Exception:
> >> DBD::mysql::st execute failed: Duplicate entry
> > 
> > My initial response to this was the same as everybody else's, "catch the damn
> > exception".
> > 
> > My second response was "can't we make this atomic somehow?" ... but of course
> > the answer is no. We could do transaction stuff and ... throw a different
> > exception.
> > 
> > I don't like your "return -1" approach though.
> > 
> > Three possiblities:
> > 
> > (1) trap duplicate key exception and do what you describe
> >     - do DBs give a sanely trappable exception here?
> > 
> > (2) try the re-select no matter what the exception
> >     - actually -probably- safe. performance issues?
> 
> Ha ha, unless you're using DBD::SQLite 1.13, then the key violation
> throws and exception and the next call fails with the same error, even
> when it's an unrelated query like a select. Gebus, what a retarded bug
> find weekend that was. :-)

I fixed that. Unfortunately I ended up with a segfault somewhere else. One
day when I'm feeling masochistic I'll try again.

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