Ruby On Rails - DB Structure for saving CRUD operation parameter/payload - ruby-on-rails

Question

What I want
I want to make a form to save "CRUD operation Infomation itself" in my database.
e.g.)
①create new row {"name": "Tom", "price": 200}
②find a row WHERE {"age": 30}
③delete row WHERE {"name": "John"}
④update the row WHERE {"name": "Ted"} SET {"price": 300}
My idea
To realize above, I created two models.
①CrudOperation
t.string :crud_type # this should be one of CRUD ("create", "read", "update", "delete")
t.string :target_database
②CrudOperationParameter
t.integer :crud_operation_id # reference
t.string :key
t.value :value
CrudOperation has many CrudOperationParameter-s.
Problem
My models seem to work well EXCEPT crud_type is "update".
like that
①create new row {"name": "Tom", "price": 200}
**CrudOperation**
id: 1
crud_type: "create"
target_database: "XXXX"
**CrudOperationParameter**
crud_operation_id: 1
key: "name"
value "Tom"
**Another CrudOperationParameter**
crud_operation_id: 1
key: "price"
value "200"
But when it comes to registering the CrudOperation with update type, the problem occurs.
④update the row WHERE {"name": "Ted"} SET {"price": 300}
**CrudOperation**
id: 1
crud_type: "update"
target_database: "XXXX"
**CrudOperationParameter**
crud_operation_id: 1
key: "name"
value "Ted"
**Another CrudOperationParameter**
crud_operation_id: 1
key: "price"
value "300"
Since CrudOperationParameter has only key-value column,
I cannot identify that this CrudOperationParameter is for WHERE clause or SET clause in UPDATE Statement.
Could you teach me better DB schema to save these kinds of data?

Answer 1

What you have is basically a half-baked version of the Entity Attribute Value pattern (or anti-pattern depending on who you are asking).
If I really had to I would set it up as:
class CrudOperation < ApplicationRecord
has_many :crud_operation_parameters
accepts_nested_attributes_for :crud_operation_parameters
enum crud_type: {
create: "create",
read: "read",
update: "update",
delete: "delete"
}
# Convenience setter that maps a hash of attributes
# into a an array of key value attibutes suitible for `accepts_nested_attributes_for`
# and sets the nested attributes
# #return [Array]
def parameters=(hash)
self.crud_operation_parameters_attributes = hash.map do |key, value|
{
key: key,
value: value
}
end
end
end
class CrudOperationParameter < ApplicationRecord
belongs_to :crud_operation
end
# 1. create new row {"name": "Tom", "price": 200}
CrudOperation.create!(
crud_type: :create,
parameters: {
name: "Tom",
price: 200
}
)
# 1. create new row {"name": "Tom", "price": 200}
CrudOperation.create!(
crud_type: :update,
parameters: {
name: "Tom",
price: 200
}
)
I mentioned that its a half baked attempt since you're lacking the Attribute table where you would normalize the definitions of attributes and store stuff like type information. Your solution instead has a string column with tons of duplicates that can become denormalized.
But modern RDBMS systems have column types such as JSON, JSONB and HSTORE which can be used instead of EAV to store data which does not fit a given schema.
Unlike EAV you don't have to store all the attributes in a single column type (usually a string) and typecast or create a bunch of attribute tables to store different types of attributes (such as StringCrudOperationParameter and FloatCrudOperationParameter).
With JSONB on Postgres I would set it up as:
# rails g model crud_operation crud_type:string payload:jsonb conditions:jsonb
class CrudOperation < ApplicationRecord
enum crud_type: {
create: "create",
read: "read",
update: "update",
delete: "delete"
}
end
# 1. create new row {"name": "Tom", "price": 200}
CrudOperation.create!(
crud_type: :create,
payload: {
name: "Tom",
price: 200
}
)
# 2. find a row WHERE {"age": 30}
CrudOperation.create!(
crud_type: :read,
conditions: {
age: 30
}
)
# 3. delete row WHERE {"name": "John"}
CrudOperation.create!(
crud_type: :delete,
conditions: {
name: "John"
}
)
# 4. update the row WHERE {"name": "Ted"} SET {"price": 300}
CrudOperation.create!(
crud_type: :update,
conditions: {
name: "John"
},
payload: {
price: 300
}
)