naktinis wrote:
> What is the best way to map several columns from one table to another
> table? Let's say I have two classes: LargeComplicatedClass and
> AnotherClass.
>
> LargeComplicatedClass which is has a lot of eager loads and columns
> with a lot of data, which is expensive to query.
>
> I also have a AnotherClass to which I want to map
> LargeComplicatedClass.title columns, so it would be many-to-many
> relationship. If I would setup a usual mapper it would look something
> like:
>
> mapper(AnotherClass, another_class_table, properties={
> 'related_large_objects': relation(LargeComplicatedClass,
> secondary=...)
> })
>
> But that would load the whole LargeComplicatedClass (I can't turn off
> eager load for that class, because usually I have to use all its
> fields, except for rare cases like this one).
>
> What I need is something like this:
>
> mapper(AnotherClass, another_class_table, properties={
> 'related_large_titles': customwhateverrelation
> ([large_complicated_table.c.title], secondary=...)
> })
>
> It is similar to column_property, except that this would be a many-to-
> many relation.
>
> Does that make sense? Or maybe I've missed some point?
you can build a second mapper for LargeComplicatedClass that doesn't have
all the eager loads - you can pass the Mapper object as the target for
relation(). The LCC instances themselves will maintain the behavior
assigned to them by their primary mapper.
>
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