single-table-inheritance

问题 I have been struggling for the past few hours thinking about which route I should go. I have a Notification model. Up until now I have used a notification_type column to manage the types but I think it will be better to create separate classes for the types of notifications as they behave differently. Right now, there are 3 ways notifications can get sent out: SMS, Twitter, Email Each notification would have: id subject message valediction sent_people_count deliver_by geotarget event_id list

问题 Say I have the following example of associations in a Rails app: I'm considering combining the *Posting models under STI. One problem with STI is the potential for many attributes that are only related to one subclass (i.e., a lot of denormalized nil values). This is especially worrisome when your subclasses and going to evolve and grow in the future. I've read a few related posts (such as this), however, as you can see in my example, the potential subclass-specific fields will not

问题 Im trying set the single table inheritance model type in a form. So i have a select menu for attribute :type and the values are the names of the STI subclasses. The problem is the error log keeps printing: WARNING: Can't mass-assign these protected attributes: type So i added "attr_accessible :type" to the model: class ContentItem < ActiveRecord::Base # needed so we can set/update :type in mass attr_accessible :position, :description, :type, :url, :youtube_id, :start_time, :end_time validates

问题 I've been playing around with STI and belongs_to / has_many relationships and I'm a bit confused. I have a few questions based on a model configuration similar to: class Parental < ActiveRecord::Base end class Mother < Parental has_many :babies end class Father < Parental has_many :babies end class Baby < ActiveRecord::Base belongs_to :?????? end What should Baby belong_to? In terms of a migration, what should i name/add for foreign key on the babies table? I've had a hard time researching

问题 In my Rails App I've several models dealing with assets (attachments, pictures, logos etc.). I'm using attachment_fu and so far I have 3 different tables for storing the information in my MySQL DB. I'm wondering if it makes a difference in the performance if I used STI and put all the information in just 1 table, using a type column and having different, inherited classes. It would be more DRY and easier to maintain, because all share many attributes and characteristics. But what's faster?

问题 I'm using Single Table Inheritance in Doctrine2 to store OAuth credentials for multiple services. I'd like to use the service's id as the primary key; however, that's not unique across all services. I've setup the database to use the discriminator column and the service's id as the primary key, but I can't find a way to make Doctrine use the discriminator column as the key (in addition to the discriminator column). I'm using docblock annotations, and if I add the discriminator column as an

问题 I found an example of how to do single table inheritance using Class mappings. http://docs.sqlalchemy.org/en/latest/orm/inheritance.html#single-table-inheritance But for the life of me, I cannot find an example of how to do this with classic mapper so that I can keep my classes and persistent mappings separate. How do I convert this example into classic mapping? I am clear on creating the tables, just not sure how to actually structure the mapper. In the example, there are the following types

问题 I'm reading about Class Table Inheritance (CTI) and finding I prefer it overall. The question I have is, is there any specific use case for Single Table Inheritance (STI) where you'd use that over CTI? I read http://rhnh.net/2010/07/02/3-reasons-why-you-should-not-use-single-table-inheritance and as far as I know, it's solid. The use case for STI being a difference in behaviour but not data. 回答1: I would like to point you to a great article I have found that explains with clarity why and when

问题 We have to create a request system which will have roughly 10 different types of requests. All of these requests will belong to the 'accounting' aspect of our application. Therefore we've called them "Accounting requests". All requests share maybe only a few columns and each has up to 20 columns individually. We started to wonder if having separate tables for each request type would be practical in terms of speed when we start to have to do very complicated joins or queries, for example,

问题 I have a model for a company. Then I have a base model for company posts. It contains common posts attributes. An attribute is the company that publishes the posts. It refers to the Company model with a ForeignKey. Finally I have a child model (based on the CompanyPost base model) for posts of type A: class Company(models.Model): name = models.CharField(...) ... class CompanyPost(models.Model): company = models.ForeignKey(Company,...) ... class PostA(CompanyPost): name = ... In a template I