In this chapter, we'll explore how to use PostgreSQL JSONB columns and the
ActiveRecord Store module in Rails. We'll start by discussing what JSONB columns
are and why they're useful, then move on to how to use them in Rails with the
ActiveRecord's store and store_accessor.
What is a PostgreSQL JSONB column?
PostgreSQL is a popular relational database management system that supports a
wide range of data types, including JSONB. JSONB stands for "JSON Binary" and is
a binary representation of JSON data that allows for efficient storage and
retrieval of complex data structures.
JSONB columns in PostgreSQL allow you to store semi-structured data as a single
column in your database table. This can be useful when you have data that
doesn't fit neatly into traditional relational database tables, such as nested
or variable-length data structures.
For example, let's say you have an e-commerce website where users can create
custom products with different options and configurations. Instead of creating
separate tables for each product option, you could store all the options as a
single JSONB column in your products table.
Use cases of storing JSON data in relational database columns
There are many use cases for storing JSON data in a database column. Here are a
few examples:
-
Storing user preferences: You can store user preferences in a single column,
such as their preferred language, timezone, or theme. This allows you to
easily retrieve and update these preferences without having to create
separate columns for each one.
-
Storing metadata: You can store metadata about a model, such as the date it
was last updated, the number of times it has been viewed, or any other
information that doesn't fit neatly into a single column.
-
Storing configuration settings: You can store configuration settings for your
application, such as the number of items per page in a paginated list or the
default sort order for a table.
-
Storing complex data structures: You can store complex data structures that
don't fit neatly into a relational database schema, such as nested arrays or
hashes.
Using JSON columns in Rails
Let's say you have a users table and you want to store additional information
about each user, such as their social media profiles. Instead of creating
separate columns for each profile, say facebook, twitter, instagram etc,
you can use a JSONB column to store all the profiles in a single column if you
have a database like PostgreSQL that supports JSONB columns.
Here's an example migration that adds a profiles JSONB column to the users
table:
Once you've created the JSONB column, you can use it to store social media
profiles for each user. Let us manually define the getter and setter methods for
each social media profile.
With this setup, you can create new users with social media profiles like this:
You can also retrieve individual profiles using the generated getter methods:
Although this works, there is a catch. Manually defining getter and setter
methods for each attribute in a JSON column can become cumbersome and difficult
to maintain as the number of attributes grows. This is because you have to write
a separate method for each attribute, which can quickly become unwieldy. This
necessitates the need for a more scalable solution that automatically generates
getter and setter methods for each attribute in a JSON column.
store and store_accessor
ActiveRecord's store and store_accessor methods provide a convenient way to
store semi-structured data, such as JSON or YAML, in a database column. When
storing JSON data in the database, there are two key aspects to consider:
serialization and access.
If you're using a json-type column in your database, like a JSONB column in
PostgreSQL, then you don't need to worry about the serialization aspect. Rails
and the database adapter will automatically handle the serialization of your
data for you. In this case, you can use the store_accessor method to define
getter and setter methods for specific attributes within your JSON data.
Here's an example model that uses the store_accessor method to generate getter
and setter methods for each profile.
With this, you can create new users with social media profiles and retrieve them
just like you did in the previous section.
Now, if you're storing your JSON data in a text column, then you'll need to
manually handle the serialization of your data. This is where ActiveRecord's
store method comes in handy. The store method automatically
serializes/deserializes your data into your chosen format when reading from or
writing to the column.
Here's an example model that uses the store method to generate getter and
setter methods for each profile.
With this, you can also create new users with social media profiles and retrieve
them just like you did in the previous section.
In summary, whether you should use store_accessor or store depends on
whether you're using a json-type column or a text column to store your JSON
data. If you're using a json-type column, then use store_accessor. If you're
using a text column, then use store.
JSON data storage best practices in PostgreSQL
When storing JSON data in a PostgreSQL database column, like JSONB, careful considerations are essential, as it may not be the best option in the following situations:
-
When you need to perform complex queries on the JSON data: While PostgreSQL
provides some powerful functions for querying JSON data, it can be difficult
to write complex queries that involve nested objects or arrays. In such
cases, it may be better to store the data in a traditional relational format.
-
When you need to enforce strict schema validation: JSON is a flexible format
that allows for arbitrary keys and values, which can make it difficult to
enforce strict schema validation. If you need to ensure that your data
conforms to a specific schema, it may be better to use a traditional
relational format.
-
When you need to perform frequent updates on individual keys within the JSON
object: Updating individual keys within a JSON object requires rewriting the
entire object, which can be inefficient if you need to perform frequent
updates on individual keys. In such cases, it may be better to store the data
in separate columns.
-
When you need to ensure referential integrity: If your application requires
referential integrity between different tables, storing JSON data in a single
column can make it difficult or impossible to enforce those constraints.
-
When you need strong typing and validation: If your application requires
strong typing and validation of data, storing JSON data in a PostgreSQL
database column like JSONB may not provide enough type safety and validation
capabilities.
In summary, while storing JSON data in a PostgreSQL database column like JSONB
can provide flexibility and ease of use, there are scenarios where using
traditional relational formats may be more appropriate due to their stronger
typing and validation capabilities or when complex queries are required.