ruby on rails 3 - Limit ignored when used with find_by_id -

i trying understand behaviour of rails activerecord limit.

let's have model car 1 attribute name.

now in console (rails console), if type:

car.limit(0).where(name: 'foo') 

i get

select "cars".* "cars" "cars"."name" = 'foo' limit 0 

which correct, but:

car.limit(0).find_by_id(1) 

gives

select "cars".* "cars" "cars"."id" = 1 limit 1 

why limit option ignored?

note that

car.where(name:'foo').find_by_id(1) 

gives

select "cars".* "cars" "cars"."name" = 'foo' , "cars"."id" = 1 limit 1 

so find_by_id(or find) ignores limit accepts where? how explain that?

sidenote

i know these queries don't make sense. have edge case in project executes car.limit(0).find_by_id(1), expected result nil object. trying understand why find_by_id or find ignores limit.

find , find_by_ methods used retrieve single instance. result either 1 object or nil if there no objects found.

because method supposed return 1 object sets limit 1 regardless of limit specify.

if want specify limit, use per example.