Is it possible to use Elasticsearch as database for a Rails Application?
I have gone through many sites, blogs, and videos to find the answer of this, but was unable to and this being the closest.
I am not sure how can it be done, what goes in the database/config.yml and will the schema be getting generated after migrate?
Yes, of course it is, but you cannot use ActiveRecord ORM, basically you'll have to create your own adapter.
If you want to go quick, I would advise you to create the activerecord models, just like any regular app, then use Searchkick and create mappings from your models.
You need to be aware that if you're not using a database to hold the values you'll need to create a repository to handle the CRUD operations in Elasticsearch.
Another option is to use https://github.com/elastic/elasticsearch-rails, but in both cases you need to have the Rails models.
If you really want to go for ElasticSearch only, in you controllers you need to call your own created repositories to fetch and save the records in ElasticSearch.
No, only these databases: MySQL, PostgreSQL, SQLite are supported if you want to use ActiveRecord, and there are also mappers for Mongo and the like.
There are some mappers and adapters out there though but I wouldn't touch them with a 10 foot barge pole - some things just shouldn't exist in this world.
Related
I have started a rails project on top of a legacy database. Standard practices required to use an ORM, like assigning ID field to each table, haven't been followed. So, I will not be creating all the models matching all the table. I need to run queries joining multiple tables using numerous conditions. I will mostly be using Model.find_by_sql or Model.connection.select_all methods. Where should I put these queries? Should I stash these in one of the models I have created that is involved in the query?
What's the standard practice for such a situation?
As much as possible, you still want to insulate the rest of your application from the details of the database by putting your queries and whatnot into the model layer. So yes, "stashing" in the right model object relevant to what you're trying to do seems like the right thing.
Are you allowed to change the schema of the database? If so, you may want to use migrations to slowly make your database look more like a standard ActiveRecord backing store.
You may also want to look into alternatives to ActiveRecord such as Sequel.
It is good idea to place the sql queries under sql folder under db. You need to create the sql folder.
I want to create an website where users can create their own teaching resources, e.g. blocks of text with embedded images etc.
How should I store this in a database in rails? I've heard mongoDB is good for storing documents but I was planning on using postgresql for the user database etc. and have read that generally you shouldn't mix different types of db
I'm sure this is an obvious question but I couldn't find an answer anywhere...
Thanks,
Graham
There are several things you could do.
1. Use PostgreSQL for both the Users table and the TeachingResources table. You could simply use a content column of type text to save all the data.
2. Use PostgreSQL but use the HStore functionality to basically store a hash of objects of your choosing, this gives you more flexibility. Rails 4 will support this by default, but there is also a gem you can use.
3. Use a combination of PostgreSQL and MongoDB (or any other NoSQL solution) in your app. I don't see this as a bad solution, but it does put you outside of the "new user constraints" in Rails, so this might not be the best route to start with
4. Go NoSQL all the way. There is no reason you shouldn't be able to use MongoDB for your User model. However, you are right that this type of datastorage can not give full ACID guarantees, so be careful with product planning and know it's vulnerabilities (but also its strengths).
Can I use MongoDB and a PostgreSQL in one rails app? Specifically I will eventually want to use something like MongoHQ. So far I have failed to get this working in experimentation. And it concerns me that the MongoDB documentation specifically says I have to disable ActiveRecord. Any advice would be appreciated.
You don't need to disable ActiveRecord to use MongoDB. Check out Mongoid and just add the gem plus any models along side any of your existing ActiveRecord models. You should note that MongoHQ is just a hosting service for MongoDB and can be used alongside any Object Document Mapper (ODM).
For further details check http://mongoid.org/en/mongoid/docs/installation.html. Just skip the optional 'Getting Rid of Active Record' step.
On a recent client site I worked with a production system that merged MySQL and MongoDB data with a single Java app. To be honest, it was a nightmare. To join data between the two databases required complex Java data structures and lots of code, which is actually databases do best.
One use-case for a two database system is to have the pure transactional data in the SQL database, and the aggregate the data into MongoDB for reporting etc. In fact this had been the original plan at the client, but along the way the databases became interrelated for transactional data.
The system has become so difficult to maintain that is is planned to be scrapped and replaced with a MongoDB-only solution (using Meteor.js).
Postgres has excellent support for JSON documents via it's jsonb datatype, and it is fully supported under Rails 4.2, out of the box. I have also worked with this and I find it a breeze, and I would recommend this approach.
This allows an easy mix of SQL and NoSQL transactions, eg
select id, blast_results::json#>'{"BlastOutput2","report","results","search","hits"}'
from blast_caches
where id in
(select primer_left_blast_cache_id
from primer3_output_pairs where id in (185423,185422,185421,185420,185419) )
It doesn't offer the full MongoDB data manipulation features, but probably is enough for most needs.
Some useful links here:
http://nandovieira.com/using-postgresql-and-jsonb-with-ruby-on-rails
https://dockyard.com/blog/2014/05/27/avoid-rails-when-generating-json-responses-with-postgresql
There are also reports that it can outperform MongoDB on json:
http://www.slideshare.net/EnterpriseDB/the-nosql-way-in-postgres
Another option would be to move your Rails app entirely to MongoDB, and Rails has very good support for MongoDB.
I would not recommend running two databases, based on personal observations on how it can go bad.
My Rails app (let's call it "Mira") will be interfacing with an existing app (let's call it "Jira"). Mira will store information about Jira and will be able to directly manipulate its database (because Jira, we'll say, has an incomplete API).
Since I want to directly manipulate Jira's database, it makes sense to have models representing each of Jira's tables in my Mira app. That way I can use ActiveRecord to manipulate it.
But in fact! There are two Jiras. A Staging instance and a Production instance.
So now I want my model that was happily interfacing with one instance of Jira to be able to use a different database.
It would be super sweet if I could do this when I instantiate my model, perhaps like this:
Jira::CustomField.new(:staging)
or something like that.
Thoughts? Better ways to accomplish this? Is my goal as stated even possible?
As the documentation for ActiveRecord::Base discusses, it is easy to have different Rails model objects connecting to different databases using the establish_connection method.
However, if you want the same class to connect to multiple databases based on configuration, that will be kind of a pain. Do you need to use ActiveRecord here or could you use DataMapper? That would work better in this scenario I think. Check out What ORM to use in one process multiple db connections sinatra application? for an example
I have a 'legacy' DB2 database that has many other applications and users. Trying to experiment with a rails app. Got everything working great with the ibm_db driver.
Problem is that I have some tables like schema1.products, schema1.sales and other tables like schema2.employees and schema2.payroll.
In the ibm_db adapter connection, I specify a schema, like schema1 or schema2, and I can work within that one schema, but I need to be able to easily (and transparently) reference both schemas basically interchangeably. I don't want to break the other apps, and the SQL I would normally write against DB2 doesn't have any of these restrictions (schemas can be mixed in SQL against DB2 without any trouble at all).
I would like to just specify table names as "schema1.products" for example and be done with it, but that doesn't seem to jive with the "rails way" of going about it.
Suggestions?
Schemas in DB2 are a very handy way to provide separate namespace to different applications. For example, you can separate all database objects for an application called "recruiting" from say application called "payroll". You can have objects (tables, views, procedures etc.) with the same name reside in multiple schemas and not colide with one another. Having your application set a schema is a handy way for it to say "hey, I am a payroll and I only want to work with my objects". So, what happens when you want to work with objects owned by another application? Well, in traditional procedural programming languages your application code would explicitly specify the schema when referencing an object in another schema or you would just do a SET CURRENT SCHEMA to switch to another schema. The problem with ORMs like ActiveRecord in Ruby on Rails is that you are not supposed to use SQL i.e. you don't have a good "Rails way" to specify schema when referencing an object. You can use find_by_sql and qualify your objects in the SQL statement but this is not what RoR people will consider to be good Rails.
You can fix things on the DB2 side. You can define a view per table in the "foreign" schema but you will have to take care to name the view so that it does not colide with what you already have in your primary schema. And, when you do that, you will undoubtedly create names that are not true Rails names.
Rails people are very proud of the "Rails way". It makes it very easy to create new applications. Rails is really awesome in this space. However, when it comes to integration with what is already out there Rails ... how do we say it ... sucks. I suggest you will have to accept to do things that are not the best examples of the Rails Way if you want to work with existing database structures.
How do i work with two different databases in rails with active records?