Ovid wrote:
> Back in the glory days (cough) of Class::DBI, lazy columns really seemed like
> a good idea in the same way that you find yourself trying why that
> one-size-fits-all suit seemed like a good idea.
>
> While you don't want to force lazy columns on every query, being able to
> specify columns lazily *per search* would be lovely, but it doesn't quite
> work. I can say:
>
> my $rs = $schema->resultset($some_class)->search(
> undef,
> { columns => ['title'] },
> );
>
> Except that I'm a nice chap and mail this off to my brother and when he opens
> it up, the first thing he sees is that the $object->wall_o_text attribute
> returns undef and he doesn't know if that's because it's undef or because I
> didn't ask for it in my "columns =>" (actually, he can know if he mucks about
> in the $rs, but it's painful).
Or he can use
http://search.cpan.org/~frew/DBIx-Class-0.08121/lib/DBIx/Class/Row.pm#has_column_loaded
>
> I'd like lazy column loading. So imagine I have a table with columns named
> 'a' to 'z' and I want to fetch everything except columns 'h','u','g' and 'e'.
>
> my $rs = $schema->resultset($some_class)->search(
> undef,
> { defer_columns => [ qw/ h u g e / ] },
> );
>
> (Or "{ '-columns' => [ qw/ h u g e / ] }"? I like that syntax, but it's not
> really the opposite of the 'columns' or '+columns' feature.)
>
> And later on:
>
> while ( my $object = $rs->next ) {
> if ( 'aye' eq $object->a ) {
> say $object->$_ for qw/ h u g e /;
> }
> }
>
> The idea is that:
>
> * $some_class must have a primary key defined
> * deferred columns must not be primary key columns
> * If a deferred column is requested, query is re-executed, asking for just
> the missing columns, using the PK as a constraint
>
> I'm sure there are serious pitfalls here, but we have an issue at work where
> deferring the loading of some columns increases SQL response time so much
> that issuing separate queries for every row to fill in missing data is faster.
>
It's not very hard, but extremely tedious to make this work transparently
the way you want. Come to #dbix-class to discuss some preliminary ideas you
have (and get them shot down in flames :D)
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