Op 16-4-2011 19:01, Robert Kinyon schreef:
On Sat, Apr 16, 2011 at 10:58, Christiaan Kras<[email protected]> wrote:
Hello list,
I've been banging my head against the wall because of an error message I'm
getting which I wasn't getting before. I'm now using DBIx::Class 0.08127,
whilst before I believe it was 0.08123.
I'm constructing my search with the following data:
my @search = (
{ 'modscope.name' => $modscope,
'me.name' => $module,
'module_versions.version' => $version,
},
{
join => [qw /modscope module_versions/],
'+columns' => ['module_versions.remote_location'],
}
);
my $rs = $c->model('DB::Module')->search(@search);
my $row = $rs->first;
...
This generates the correct query for my case. The reason I explicitly tell
it to add the module_versions.remote_location column is because the
module_versions tables contains a BLOB column that can be big. If the
remote_location appears to be empty I'll fetch it in a new call, otherwise
it redirects the user to the remote_location (this is a Catalyst
application).
In 0.08123 and 0.08124 this works as I intended and described.
In 0.08125 and 0.08127 it doesn't and I'm presented with this error message:
"Implicit prefetch (via select/columns) not supported with accessor
'multi'". The moment the database call is being made ($rs->first) the given
error message shows up.
My question is, is this a bug in DBIx::Class or am I doing something that
wasn't supposed to work from the beginning?
If this behavior is intended could one give me directions on how to refactor
my code? I'm also curious as why this change was made if this is indeed the
case.
The old behavior was a bug. What is happening is that you have a
Module->has_many(ModuleVersions). When the +columns happens, DBIC
doesn't know that there is only one possible value for
module_versions.remote_location. Your query may be able to guarantee
this, but DBIC doesn't know that when it's building the query.
The simplest fix is to remove the +columns, then traverse the
relationship. When you do that, you'll see exactly why DBIC cannot
assume anything.
Alternately, prefetch module_versions. :)
OK, that makes sense.
With prefetching am I able to exclude a column from the query? Like I
said the reason I was doing this was because one of the columns is a
BLOB. Otherwise I should perhaps look at storing this data somewhere
else (perhaps another dedicated table).
--
Christiaan Kras
http://blog.htbaa.com
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