Multiple joins to the same model using multiple belongs_to associations - ruby-on-rails

Question

I have a class Agreement that has two belongs_to associations to a Member class - referenced as primary and secondary:
class Agreement < ActiveRecord::Base
belongs_to :primary, class_name: 'Member'
belongs_to :secondary, class_name: 'Member'
...
def self.by_member(member_attribute_hash)
# returns any agreements that has a primary OR secondary member that matches any of the values
# in the member_attribute_hash
...
end
end
The Member class has no knowledge of the association with the Agreement class - it does not need to:
class Member < ActiveRecord::Base
# contains surname, given_names, member_number
...
def self.by_any(member_attribute_hash)
# returns any member where the member matches on surname OR given_names OR member_number
...
end
end
What I would like to do is search for all agreements where the primary or secondary member matches a set of criteria.
From previous work (see question #14139609), I've sorted out how to build the conditional where clause for Member.by_any().
Trying to reuse that method while search for Agreements led me to try this:
class Agreement < ActiveRecord::Base
...
def self.by_member(member_attribute_hash)
Agreement.joins{primary.outer}.merge(Member.by_any(member_attribute_hash)).joins{secondary.outer}.merge(Member.by_any(member_attribute_hash))
end
end
On running this in the console, with a member_attribute_hash = {surname: 'Freud'}, the generated SQL fails to honour the alias generated for the second join to member:
SELECT "agreements".*
FROM "agreements"
LEFT OUTER JOIN "members"
ON "members"."id" = "agreements"."primary_id"
LEFT OUTER JOIN "members" "secondarys_agreements"
ON "secondarys_agreements"."id" = "agreements"."secondary_id"
WHERE "members"."surname" ILIKE 'Freud%'
AND "members"."surname" ILIKE 'Freud%'
Notice the duplicate conditions in the WHERE clause. This will return Agreements where the primary Member has a surname like 'Freud', but ignores the secondary Member condition because the alias is not flowing through the merge.
Any ideas?

Answer 1

After struggling to understand this, I ended up replacing the Member.by_any scope with a Squeel sifter:
class Member < ActiveRecord::Base
# contains surname, given_names, member_number
...
def self.by_any(member_attribute_hash)
# returns any member where the member matches on surname OR given_names OR member_number
squeel do
[
(surname =~ "#{member[:surname]}%" if member[:surname].present?),
(given_names =~ "#{member[:given_names]}%" if member[:given_names].present?),
(member_number == member[:member_number] if member[:member_number].present?)
].compact.reduce(:|)
# compact to remove the nils, reduce to combine the cases with |
end
end
end
The only difference (code-wise), bewteen the sifter and the scope is the replacement of the where in the scope with squeel in the sifter.
So, instead of using a merge to access the Member.by_any scope from the Agreement model, I was now able to reference the Member :by_any sifter from the Agreement model. It looked like:
class Agreement < ActiveRecord::Base
...
def self.by_member(member_attribute_hash)
Agreement.joins{primary.outer}.where{primary.sift :by_any, member_attribute_hash}.joins{secondary.outer}.where{secondary.sift :by_any, member_attribute_hash}
end
end
This fixed the aliasing issue - begin celebrating!:
SELECT "agreements".*
FROM "agreements"
LEFT OUTER JOIN "members"
ON "members"."id" = "agreements"."primary_id"
LEFT OUTER JOIN "members" "secondarys_agreements"
ON "secondarys_agreements"."id" = "agreements"."secondary_id"
WHERE "members"."surname" ILIKE 'Freud%'
AND "secondarys_agreements"."surname" ILIKE 'Freud%'
but I still wasn't getting the results I expected - celebration put on hold. What was wrong? The AND in the where clause was wrong. After a bit more digging (and a night away from the computer), a refreshed mind decided to try this:
class Agreement < ActiveRecord::Base
...
def self.by_member(member_attribute_hash)
Agreement.joins{primary.outer}.joins{secondary.outer}.where{(primary.sift :by_any, member_attribute_hash) | (secondary.sift :by_any, member_attribute_hash)}
end
end
Producing this:
SELECT "agreements".*
FROM "agreements"
LEFT OUTER JOIN "members"
ON "members"."id" = "agreements"."primary_id"
LEFT OUTER JOIN "members" "secondarys_agreements"
ON "secondarys_agreements"."id" = "agreements"."secondary_id"
WHERE ((("members"."surname" ILIKE 'Freud%')
OR ("secondarys_agreements"."surname" ILIKE 'Freud%')))
Ah sweet... restart celebration... now I get Agreements that have a primary or secondary Member that matches according to the rules defined in a single sifter.
And for all the work he's done on Squeel, a big shout-out goes to Ernie Miller.