Rails core - Nov 2014 - Should find_by_<attr>(nil) make no queries if db has NOT NULL constraint?

Current behavior:

User.find_by_id(nil)
User Load (1.1ms)  SELECT  "users".* FROM "users"  WHERE
"users"."id" IS
NULL LIMIT 1

User.find_by_id("")
User Load (0.6ms)  SELECT  "users".* FROM "users"  WHERE
"users"."id" = 0
LIMIT 1

I realize it's hard to always be able to tell whether given parameter can 
exist or not, but above cases seem like pretty obvious, and also the most 
common cases (e.g. accepting blank param from request), or chaining queries 
where previous query returned nil.

Interestingly enough, User.find(nil) raises right away without queries, but 
not User.find_by_id(nil).

I noticed my code often ends up like:

User.find_by_id(id) if id.present?

This seems like unnecessary cruft that the app should in many cases know on 
its own, at least in following cases:

   - Looking up nil on column which has NOT NULL constraint.
   - Looking up blank string on integer db field (common when passing 
   request param to query). This will be casted to 0, but unlike explicit 
   find_by_id(0), which theoretically could exist in db via manual insertion, 
   I think it's safe to assume that anyone passing blank string to
find_by_id
   and friends should expect it to be treated as nil and not 0.

Could Rails check the db schema and know whether nil/blank values are 
possible in db? If not, it could short-circuit or use NullScope to avoid 
making unnecessary query.

Thanks!

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Core" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to rubyonrails-core+unsubscribe@googlegroups.com.
To post to this group, send email to rubyonrails-core@googlegroups.com.
Visit this group at http://groups.google.com/group/rubyonrails-core.
For more options, visit https://groups.google.com/d/optout.