BTW:
http://search.cpan.org/~ash/DBIx-Class-0.08008/lib/DBIx/Class/ResultSet.pm#ATTRIBUTES
doesn't contain the "key" attribute.
Am 15.01.2008 um 08:00 schrieb Zbigniew Lukasiak:
On Jan 14, 2008 10:59 PM, Jason Kohles <[EMAIL PROTECTED]> wrote:
On Jan 14, 2008, at 2:19 PM, Zbigniew Lukasiak wrote:
On Jan 13, 2008 7:20 PM, Matt S Trout <[EMAIL PROTECTED]>
wrote:
On Sun, Jan 13, 2008 at 10:41:43AM +0100, Patrick Weemeeuw wrote:
There is a small bug in find_or_new: when the find part
fails, it calls new_result with the hash containing the
values that were used for the search. It should use no
values at all instead.
This isn't a bug. If that's the behaviour you want, do
my $o = $rs->find({ id => $id }) || $rs->new({});
Example buggy case: $o = $...->find_or_new( { id => $id } )
with id a not null primary key. When $id is undefined, there
is obviously no row in the DB, and a new result object is
returned. However, the object returned contains the column
id => NULL, which (1) is invalid for this kind of object,
and (2) prevents in some backends (e.g. Pg) that the
sequence is used to generate a unique id.
So don't pass id if it isn't a valid value. Passing undef there is
a bug
in your code, not in DBIx::Class.
The usual use of find_or_new is to pass a unique key plus
additional
attributes to be used for object creation (which are ignored in the
find()
by specifying the key attr as well). Consider for example
my $stats = $schema->resultset('PageViews')->find_or_new(
{ page => $page, views => 0 },
{ key => 'page' }
);
How can we excercise the _or_new part of find_or_new?
The results you are seeing are *exactly* the way it is expected to
work. In this example you are doing:
$rs->find_or_new( { id => undef } )
and getting back an object where id is undefined. How is that
mysterious or incorrect behaviour? You told it 'find me a row in the
database where id is undef, and if you can't find one, create a new
object where id is undef' and that's exactly what it did.
The big difference between ->find_or_new and ->find_or_create, is
that
->find_or_new doesn't attempt to do the insert yet, and so is not
guaranteed to return to you an object that even *can* be inserted.
What I would do in this case is either not use ->find_or_new when you
don't have a valid primary key, or do something like this:
my $obj = $rs->find_or_new( $id ? { id => $id } : {} );
or even...
my $obj = $rs->find_or_new( { id => $id } );
if ( ! defined $obj->id ) { $obj->id( 'foo' ) }
From the above I conclude that we should omit 'page' in the request
(instead of setting it to 'undef'):
my $stats = $schema->resultset('PageViews')->find_or_new(
{ views => 0 },
{ key => 'page' }
);
but then if we have another record with views == 0 it will be found
and no new row would be created.
You've just created an even more bizarre situation, what you have now
is essentially
my $rs = $schema->resultset( 'PageViews' );
my $stats = $rs->find( {} ) || $rs->new( { views => 0 } );
The documentation for find_or_create says "Tries to find a record
based on its primary key or unique constraint; if none is found,
creates one and returns that instead." What you are trying to do is
use it without providing a primary key or a unique constraint, and
the
behavior you are seeing is exactly what I would expect to happen in
that situation, since ->find can't match anything without a primary
key or a unique constraint, you get back a new object instead.
No - that is not what would happen. No new record will be created if
you have another record that have views == 0.
This is very important - the behaviour is not what is documented - but
it is intentional - as the comment in the code shows.
--
Zbigniew
This is because find falls back on finding by all columns in the
query
(ie by 'views' in this case)
if the key is not represented in the query - this is not documented,
but it is commented in the source:
# @unique_queries = () if there is no 'key' in $input_query
# Build the final query: Default to the disjunction of the unique
queries,
# but allow the input query in case the ResultSet defines the query
or the
# user is abusing find
my $alias = exists $attrs->{alias} ? $attrs->{alias} : $self-
>{attrs}
{alias};
my $query = @unique_queries
? [ map { $self->_add_alias($_, $alias) } @unique_queries ]
: $self->_add_alias($input_query, $alias);
I would say - we should get rid of that 'special feature'.
I would say it's working exactly as intended, you are abusing find
and
it's doing the best it can to accomodate you, by creating new objects
when your ->find fails to find a matching row. The only
alternative I
can see would be for it to throw an exception when you try and call
find_or_create without the
--
Jason Kohles, RHCA RHCDS RHCE
[EMAIL PROTECTED] - http://www.jasonkohles.com/
"A witty saying proves nothing." -- Voltaire
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--
Zbigniew Lukasiak
http://brudnopis.blogspot.com/
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