How to join on subqueries using ARel?

Question

I have a few massive SQL request involving join across various models in my rails application. A single request can involve 6 to 10 tables.

To run the request faster I w

Answer 1

OK so my main problem was that you can't join a Arel::SelectManager ... BUT you can join a table aliasing. So to generate the request in my comment above:

a = A.arel_table
b = B.arel_table

subquery = B.select(:a_id).where{c > 4}
query = A.join(subquery.as('B')).on(b[:a_id].eq(a[:id])
query.to_sql # SELECT A.* INNER JOIN (SELECT B.a_id FROM B WHERE B.c > 4) B ON A.id = B.a_id