Improve eager_loading performance

[exseniorastronaut]

It would be nice if somehow we could eager_load non recursive relations on their own go-routine to speed up the process. For example if you are eager_loading 6,7 relations this would improve the performance significally.

[aarondl]

Perhaps this can be part of the eager loading rewrite which is sorely needed.

[ccakes]

Is it possible at all to preload using SQL JOINs instead of the additional queries? This is how ORMs in other languages tend to handle preloading, I'm new to Go but any that do support a form of preloading do so using multiple queries.

[aarondl]

It most likely is. But note that it's not the case for to-many relationships. Most ORMs (things like ActiveRecord included) will do separate queries instead of left joins because otherwise you get the difficult-to-deal with sql output:

car happy
red 2
red 5
red 6