So as I was following the Ruby on Rails Tutorial by Michael Hartl I noticed that in the users table we added a unique index for the :email attribute to improve the efficiency of the find method so it doesn't search row by row. So far we have been searching using both find_by_email and find_by_id depending on the case. Yet we never set up an index for the :id attribute. Is :id automatically indexed because it is by default unique and sequential in nature? Or is this not the case and should I add an index for :id searching?
Most databases (sqlite included, which is the default db in RoR) automatically index the primary key, which with Rails Migrations is :id by default.
Related
I have a case where one model is related 2 other ones. I am trying to correctly setup the model relationships between these 3 models.
A simplified example... The first 2 tables are clients and invoices:
db.create_table(:clients) do
primary_key :id
String :name
end
db.create_table(:invoices) do
primary_key :id
String :description
Integer :balance
end
A third table, called files, contains records for files which can be related to either clients or invoices:
db.create_table(:files) do
primary_key :id
String :name
String :path
String :type # [image, pdf, word, excel]
end
There are 2 joiner tables to connect files to clients and invoices:
db.create_table(:clients_files) do
Integer :client_id
Integer :file_id
end
db.create_table(:files_invoices) do
Integer :invoice_id
Integer :file_id
end
The question is, how to correctly set up the relationships in the models, such that each client and invoice can have one or more related files?
I can accomplish this using many_to_many and has_many :through associations, however, this doesn't seem to be the right approach, because a given file can belong to only one customer or invoice, not to many.
I can also do this using polymorphism, but the documentation discourages this approach:
Sequel discourages the use of polymorphic associations, which is the
reason they are not supported by default. All polymorphic associations
can be made non-polymorphic by using additional tables and/or columns
instead of having a column containing the associated class name as a
string.
Polymorphic associations break referential integrity and are
significantly more complex than non-polymorphic associations, so their
use is not recommended unless you are stuck with an existing design
that uses them.
The more correct association would be one_to_many_through or many_to_one_through, but I can't find the right way to do this. Is there a vanilla Sequel way to achieve this, or is there a model plugin that provides this functionality?
With your current schema, you just want to use a many_to_many association to files:
Client.many_to_many :files
Invoice.many_to_many :files
To make sure each file can only have a single client/invoice, you can make file_id the primary key of clients_files and files_invoices (a plain unique constraint/index would also work). Then you can use one_through_one:
File.one_through_one :client
File.one_through_one :invoice
Note that this still allows a File to be associated to both a client and an invoice. If you want to prevent that, you need to change your schema. You could move the client_id and invoice_id foreign keys to the files table (or use a single join table with both keys), and have a check constraint that checks that only one of them is set.
Note that the main reason to avoid polymorphic keys (in addition to complexity), is that it allows the database to enforce referential integrity. With your current join tables, you aren't creating foreign keys, just integer fields, so you aren't enforcing referential integrity.
When I have a column named "fullname" in the existing model, I want to set a limit of 50 characters to store in that column. What is the best method to achieve this? Use rails migrate? or code something in app/models to do syntax checking?
You should really do both. You want your database to enforce your data restrictions as this prevents any bugs in your application code from allowing invalid data. Create a rails migration to alter the data type of your column. For example...
change_table :table_name do |t|
t.change :column_name, :string, :limit => 50
end
You should also ensure the data is less than 50 characters in your application code, otherwise you will get an error if you try to insert a value greater than 50 characters. The rails way to do this would be an Active Record Validation in your model. See this link for info on Active Record validations
I'm using DataMapper connected to an SQLite backend. I need to create a Unique index across my four belongs_to columns. Here is the table.
class Score
include DataMapper::Resource
property :id, Serial
property :score, Integer
belongs_to :pageant
belongs_to :candidate
belongs_to :category
belongs_to :judge
#What we want is a UNIQUE INDEX on the four properties!
end
Things I've done:
A unique index on the four via something like :unique_index => :single_score. This works only if you have a property already included.
validates_uniqueness_of, I think the scope only works for a 2-column unique index.
My current solution, which is to just create a dummy field "dont_mind_me", just so I can put :unique_index => single_score in it and everything works. Is this something that's okay to do?
Create an index using raw SQL, SQLite supports a unique index among the four fields.
Basically there are two parts of this question:
Is my solution okay, or should I find another one? I'm at wit's end dealing with what seems to be something trivial, even with raw SQL
How do I create an "after_create_table" hook in DataMapper? The hooks in the documentation only tell about post-CRUD data.
I have a question.
Devise and mailboxer are installed on my rails app without any problem.
The problem is that you have to use "email" or "name" column to associate devise user with mailboxer.
Obviously, devise doesn't have column called "name" in Users table.
So, if you use "email" then users will see everyone else's email address that they wanna hide.
I want twitter-like registration.
They've got unique_id(account name) that never will be changed.
To achieve that, How can I?
I. Add column named "unique_id" to Users table?
command: rails g migration AddUniqueIdToUsers unique_id:string
to create migration file, and open and edit like this
class AddUniqueIdToUsers < ActiveRecord::Migration
def change
add_column :users, :unique_id, :string
add_index :users, :unique_id, :unique => true
end
end
II. How do I associate devise with mailboxer by using "unique_id" column?
Thanks in advance
Obviously, devise doesn't have column called "name" in Users table
That is entirely up to you, all Devise does (or wants you to do) is add a few records that tell it how to function. If you look at the devise generator you can see that all it does is add a couple of columns to your migration.
I want twitter-like registration. They've got unique_id(account name) that never will be changed. To achieve that, How can I?
First of all, a unique ID is always given to you by free in Rails (indeed, in most typical web applications using a database backend, each row has a unique ID).
But, if you also want users to select a username, and have that be unique as well, the you could do as the mailboxer readme states and simply override the usage of name with your own database column like username, like so:
Mailboxer.setup do |config|
# ...
#Configures the methods needed by mailboxer
config.email_method = :email
config.name_method = :username
# ...
end
Or, if you want to stay out of the mailboxer config file, you can simply use alias_method and do this (given that you have a username column):
class User < ActiveRecord::Base
alias_method :name, :username
acts_as_messageable
end
Either way, Devise doesn't restrict you in which columns you use on your User model, and it seems that Mailboxer also doesn't restrict you in which columns you use to attach the gem to the User model. So you have as much flexibility as you want without having to built this functionality by yourself.
I am working on a sinatra app with datamapper connected to a mysql database and am having problems retrieving/finding records from only one specific table. I can insert into it with datamapper find but when I try to do #sleepEntries = Sleep_Log.all I get the following error: ArgumentError: argument out of range. When I load everything into irb I get the same error. I also turned on the ability to see the queries and I get back SELECT id, start_time, length, timestamp FROM sleep_logs ORDER BY id when I call Sleep_Log.all. When I connect to the mysql database through the mysql command line tool I can confirm that there are entries in that table. When I run the query that datamapper is erroring out on I have no problem getting the results. Here is my datamapper model info for Sleep_Log
class Sleep_Log
include DataMapper::Resource
property :id, Serial
property :start_time, Time, :required => true
property :length, Integer, :required => true
property :timestamp, DateTime, :writer => :private
belongs_to :user
end
This is what the table looks like in the database accessed through describe sleep_logs;
What is weird is that retrieve results from all other tables.
The backtrace from irb
If you try Sleep_Log.first, do you get the error? If so, could you paste in the record, or one which also shows the error?
How was the table constructed? Are you using DM to inspect already entered records? Or are you entering them through DM too?
We just encountered the exact same problem. In our case it turned out that you have to use DateTime. Mysql doesn't have a Time database type and saves as DateTime. However, DataMapper doesn't get it and blows up. If you switch your model to use DateTime DM will get it.