Rails 2.3中的自定义唯一性验证

Question

I'm trying to write a validation in Rails 2.3.

I have two fields, let's call them record_id and user_id.

The record_id will have both a user_id associated as well as a Name property.

The validation should check that when a user creates a new record, that the Name property hasn't already been used. If the user_id is the same BUT the record_id is different, an error should be raised when a user tries to enter a non-unique Name.

If the record_id and user_id is the same and the user tries to create a Name that's already in the database, then the user should be allowed to user a Name that's already in use.

I'm fairly new to Rails 2.3 so ANY guidance at all is most appreciated.

Answer 1

那么...您想允许每个用户使用多个名称，检查用户名称是否重复？

validates_uniqueness_of :name, :scope => :user_id

Answer 2

Add unique index on [:user_id, :name] on database side.

validate_uniqueness has a heavy performance impact - it adds select on any record create or update, and, in reality, does not guarantee anything for concurrent updated