Add support for joins

[sorinstanila]

Do you think we need more to have support for joins?

[vlucas]

I am not opposed to supporting joins, but I think doing is this way would be problematic for a number of reasons:

• Spot uses custom syntax for WHERE conditions that is simpler than what DBAL wants. Any official JOIN support would have to use the known Spot syntax and translate it to the JOIN.
• Fields in Spot can have aliases that need to be accounted for in JOIN conditions and columns
• It probably should be possible to JOIN on a Spot Entity class name in addition to a raw table name
• ... and many other concerns like that.

The primary reason Spot doesn't support them right now is that in general, I feel like if you are building complex queries, an ORM is not the best tool for the job, and will most likely result in an unoptimized and inefficient query. This Tweet is a prime example of what I am talking about here (happened TODAY, in fact.) https://twitter.com/naderman/status/740901123666644992

[sorinstanila]

I believe that this library has a lot of potential and missing the support for join, is one of the key feature missing( as discussed in other pull requests/issues).
Yes, of course, we can find bad example for anything related to database loading, but if do not try to improve and learn from, it would not help :)
I will look on the things you mentioned and update the requests.
Any other feedback related to the implementation is welcomed and appreciated :)

[vlucas]

I agree that a good ORM should support joins, and would like to see them in Spot as an option for those who think differently than I do. I will help you work through it and support you all I can. I am looking forward to seeing what you come up with. 👍

[sorinstanila]

I am also want to add eager loading of entities/mappers which are selected with the join. Right now is only populated the mapper which the join is created.
It still need to add some tests.

[vlucas]

Don't worry about the eager loading of relations for now - that is enough work for a separate PR after JOIN support is in (if it is even needed at all).

[mdular]

+1! :)

[sorinstanila]

Sorry all for the long time awaiting this.
I broke my arm and I am still in recovery period. In 3 weeks I hope to get back :)

[luklub]

+1
The lack of this feature is very noticeable.

[vlucas]

Should this be done at a higher level since all these are the same? i.e. do this before passing in the $value to the type classes.

[vlucas]

I don't see any tests for the actual JOIN methods. Those need to be added to merge a feature that adds support for JOINs.