Discussion: remove foreign keys

[i-norden]

Pros:

• Referential integrity enforced inside the database
• Referential data guarantee can allow a more performant query to be used in some cases
• CASCADE DELETEs (when used properly to minimize and/or simplify DELETE queries; shift work to the server)
• Ramil: Referencing by SERIAL (INTEGER) id uses less storage than referencing by 32 byte hashes (VARCHAR(66))

Cons:

• Performance overhead on INSERTs due to lookup to confirm fk exists
• Makes sharding the database more difficult
• Can make testing more difficult as test data must include fk table data
• CASCADE DELETEs (potential pitfall; developers/operators need to be aware of the side effects of their DELETEs)