I'm designing a ruby on rails app for a pharmacy, and one of the features is that there are stores who have pharmacists who work there. In addition, there are pharmacists, who can work at many stores. This sounds like a job for HABTM, right? Well, being the novice I am, I manually designed a workaround (because I never heard of HABTM - I basically taught myself rails and never got to some of the more advanced relationships). Right now, when a pharmacist is saved, there's a couple of lines in the create and update action of the pharmacists controller that turns the stores that they work at into a string, with each store_id separated by a comma. Then, when a store is displayed, it does a MYSQL request by
#pharmacists = Pharmacist.find :all, :conditions => "stores REGEXP '#{#store.id}'"
Would moving this system over to a rails based HABTM system be more efficient? Of course it would require less code in the end, but would it be worth it? In other words, what benefits, other than less code, would I get from moving this association to be managed by rails?
The benefit is that you will be using the right tool for the job! The whole point of using a framework such as Rails is that it helps you solve common problems without having to re-invent the wheel, which is what you've done here. By using associations you'll also be using a relational database properly and can take advantage of benefits like foreign key indexing, which will be faster than string manipulation.
You should use a has_and_belongs_to_many relationship unless you need to store extra attributes on the join model (for example the date a pharmacist started working at a store) in which case use has_many :through.
Using Rails associations will give you all the convenient methods that Rails provides, such as these:
# Find the stores the first pharmacist works at
#stores = Pharmacist.first.stores
# Find the pharmacists who work at a store
#pharmacists = Store.find_by_name('A Store').pharmacists
A Guide to ActiveRecord Associations
Related
First of all, I'm not a native English speaker, so excuse me if I make any mistakes related to my writing.
I'm starting as a dev and I was told that I should use a Postgresql query to accomplish a specific task in Ruby on Rails. This is the query:
ORDER BY array_position(ARRAY[1, 2, 3], spree_products.id)
The goal is to show a view with different Spree products (probably the "ARRAY[1,2,3, etc]" part) of the database ordered in the same way they are placed in an input of an admin form.
Anyway, my question is more simple than that.
I understand this query is raw Postgresql, using an array_position function
https://www.postgresql.org/docs/12/functions-array.html
I just want to know how can I implement this kind of raw queries in Rails. It probably has to be in an .rb file, but I don't really understand how, since query methods used in Rails (.order, for example) are much more common to see being used (that's what I commonly use), but apparently, here I should use raw Postgresql mixed with Rails.
Can you give me some examples and/or a basic documentation, please? I know the basics of both languages, but I've never mixed them in this way, so that's what is probably confusing me the most.
Thank you all.
you could create a scope and use arel wrap the array function array_position
class Product < ApplicationRecord
scope :order_ids, ->(arr_ids) {
order(Arel.sql("array_position(ARRAY#{arr_ids}, id::integer)"))
}
end
now you could query as below
Product.order_ids([3,2,1])
Product.where(active: true).order_ids([3,2,1]).limit(10)
# ...
I have a model and table that I believe is perfectly suited to STI. My table is called Finances and has two types: Income and Expenses. Besides type there are three other columns: description, amount, and date.
I'm getting very nervous using STI in Rails, since it requires some hacking. I'm too new to Rails to hack up the code. Even though it works, I don't understand it. That seems dangerous.
My question is, how do I set up my model, controller, and view if I do NOT use STI? Any best practices to group items in my model? Or do I just do Finances.where("type = 'Income'") before setting up a view?
Edit: I made a gist to show the code I'm working with. When I run it I get the error:
undefined method `incomes_path' for #<#<Class:0x007fbc95f60b40>:0x007fbc93883220>
First, using STI is standard for Rails, so there is no need to feel nervous. And no need for "hacking".
It has been used very successfully by many developers. And as you have seen, you can find tutorials and general information on the net.
If on the other hand, you decide NOT to use STI, you have the choice of using
(a) completely separate models with their own tables, which will result in a lot of duplicated code, or
(b) create you custom "STI-like" behaviour by hand.
The second option could at least be interesting to learn more about Rails.
For example, in your Finances model you would define a scope incomes, like
scope :incomes, where(:type => 'Income')
then you can do Finances.incomes.
Then, if you have methods that apply only to one of the types, you should check that all records effectively are of the needed type.
Personally, I would advice you to use STI. You get a lot of functionality for free and you are doing it the Rails way.
Imagine, for example, other developers reading your code, they will ask themselves, why you didn't use STI, blame it on ignorance and - if need be - refactor it using STI.
STI is best if you are using inheritance structure like this. You don't really need to use Finances.where("type = 'Income'"). You can simply use Income.all. see these posts if they help you.
http://www.therailworld.com/posts/18-Single-Table-Inheritance-with-Rails
http://juixe.com/techknow/index.php/2006/06/03/rails-single-table-inheritance/
I have a database with several tables, each one containing columns that may not follow the rails naming convention.
Is there a tool existing to create the ActiveRecord models from those tables or do I need to do this at hand, one by one ?
If I create the ActiveRecord model for one table by hand, would this be ok though ? (no hidden DB identifier needed on top of it ?)
UPDATE
I have tried magicmodels but cannot have it working (it has been a while since it was last modified) and does not seem to be compatible with rails 3.2
What I tried then:
- change the database.yml so it points towards my existing Postresql database
- manually create my models such as:
# app/models/user.rb
class User < ActiveRecord::Base
end
- run the console and tried
User.all
=> I end up with an error saying that contant User was not initialized.
Doesn't the console import the model automatically ? Or is that linked to the fact the configuration I did is not correct ?
http://magicmodels.rubyforge.org/magic_model_generator/ may be what you're looking for. I haven't heard of many tools that give this functionality, though, as many rails apps are designed from scratch instead of given a legacy db and then creating the models from that.
You can easily create models by hand and map them to pretty much any db table. Models have a "set_table_name 'name'" that lets you over-write the rails default convention of a single model mapping to a plural db table name.
ActiveRecord works OK with legacy databases. I did a back-end system that didn't use Rails with ActiveRecord as my ORM. "ActiveRecord Without Rails" got me started. "Using ActiveRecord outside Rails" is also useful. Search Google for "use activerecord without rails" and you'll find even more.
You don't need a fully fleshed out model. Just use a base class for the tables you want and ActiveRecord will query the database for what it needs. It won't know about table relationships, but for general queries it'll do fine. Build the relationships as you go and need them.
I want to structure my database in such a way that certain tables (that don't have any relationships with other tables, so no joins required) have to be put on seperate mysql databases.
I know each model has a establish_connection property.
What I want to do:
I will fetch 10 rows from a particular model, based on a clientID.
The clientID will determine which database this model will be fetched from.
I want to have this database routing logic baked into the model logic somehow.
Is this possible?
You can point individual models to different databases using establish_connection in your models. See here for examples.
If you want a single model to access multiple databases based on an attribute, you probably need to use database sharding, for example, with DataFabric or ShardTheLove.
Don't know if this can help you :
https://github.com/brianmario/mysql2
This allows you to do connections and requests like this :
client = Mysql2::Client.new(:host => "localhost", :username => "root")
results = client.query("SELECT * FROM users WHERE group='githubbers'")
Looks like what you need is 'Sharding' support
Unfortunately, ActiveRecord doesn't have this built in. There are a bunch of gems that hack in Sharding support
The gem 'octopus' seems promising. See https://github.com/tchandy/octopus
Note: I haven't used octopus myself
If you are willing to go one step further, I recommend Sequel ( http://sequel.rubyforge.org/ ) which is a stable, feature-rich ORM that I have used before.
The documentation is excellent. What you need is http://sequel.rubyforge.org/rdoc/files/doc/sharding_rdoc.html
It might take sometime to get used to Sequel if you are accustomed to AR 2.x. There is a nice migration guide. See http://sequel.rubyforge.org/rdoc/files/doc/active_record_rdoc.html
Hoping this helps
thanks for your time first...after all the searching on google, github and here, and got more confused about the big words(partition/shard/fedorate)，I figure that I have to describe the specific problem I met and ask around.
My company's databases deals with massive users and orders, so we split databases and tables in various ways, some are described below:
way database and table name shard by (maybe it's should be called partitioned by?)
YZ.X db_YZ.tb_X order serial number last three digits
YYYYMMDD. db_YYYYMMDD.tb date
YYYYMM.DD db_YYYYMM.tb_ DD date too
The basic concept is that databases and tables are seperated acording to a field(not nessissarily the primary key), and there are too many databases and too many tables, so that writing or magically generate one database.yml config for each database and one model for each table isn't possible or at least not the best solution.
I looked into drnic's magic solutions, and datafabric, and even the source code of active record, maybe I could use ERB to generate database.yml and do database connection in around filter, and maybe I could use named_scope to dynamically decide the table name for find, but update/create opertions are bounded to "self.class.quoted_table_name" so that I couldn't easily get my problem solved. And even I could generate one model for each table, because its amount is up to 30 most.
But this is just not DRY!
What I need is a clean solution like the following DSL:
class Order < ActiveRecord::Base
shard_by :order_serialno do |key|
[get_db_config_by(key), #because some or all of the databaes might share the same machine in a regular way or can be configed by a hash of regex, and it can also be a const
get_db_name_by(key),
get_tb_name_by(key),
]
end
end
Can anybody enlight me? Any help would be greatly appreciated~~~~
Case two (where only db name changes) is pretty easy to implement with DbCharmer. You need to create your own sharding method in DbCharmer, that would return a connection parameters hash based on the key.
Other two cases are not supported right away, but could be easily added to your system:
You implement sharding method that knows how to deal with database names in your sharded dabatase, this would give you an ability to do shard_for(key) calls to your model to switch db connection.
You add a method like this:
class MyModel < ActiveRecord::Base
db_magic :sharded => { :sharded_connection => :my_sharding_method }
def switch_shard(key)
set_table_name(table_for_key(key)) # switch table
shard_for(key) # switch connection
end
end
Now you could use your model like this:
MyModel.switch_shard(key).first
MyModel.switch_shard(key).count
and, considering you have shard_for(key) call results returned from the switch_shard method, you could use it like this:
m = MyModel.switch_shard(key) # Switch connection and get a connection proxy
m.first # Call any AR methods on the proxy
m.count
If you want that particular DSL, or something that matches the logic behind the legacy sharding you are going to need to dig into ActiveRecord and write a gem to give you that kind of capability. All the existing solutions that you mention were not necessarily written with your situation in mind. You may be able to bend any number of solutions to your will, but in the end you're gonna have to probably write custom code to get what you are looking for.
Sounds like, in this case, you should consider not use SQL.
If the data sets are that big and can be expressed as key/value pairs (with a little de-normalization), you should look into couchDB or other noSQL solutions.
These solutions are fast, fully scalable, and is REST based, so it is easy to grow and backup and replicate.
We all have gotten into solving all our problems with the same tool (Believe me, I try to too).
It would be much easier to switch to a noSQL solution then to rewrite activeRecord.