What is the `JSONB` data type and how do you use it in PostgreSQL?

Q: What is the `JSONB` data type and how do you use it in PostgreSQL?

Learn the answer to "What is the `JSONB` data type and how do you use it in PostgreSQL?" with detailed explanations, code examples, and best practices on DeployU.

The Scenario

You are a backend engineer at a social media company. You are building a new service that needs to store and query large amounts of JSON data.

You are considering using either a TEXT column or a JSONB column to store the JSON data.

The Challenge

Explain what the JSONB data type is in PostgreSQL and why it is a better choice than a TEXT column for storing JSON data. What are the key operators that you would use to query a JSONB column?

Wrong Approach

A junior engineer might try to store the JSON data in a `TEXT` column. This would work, but it would be very inefficient to query the data. They might not be aware of the `JSONB` data type or the special operators that can be used to query it.

Addresses symptoms, not root cause

Right Approach

A senior engineer would know that `JSONB` is the perfect tool for this job. They would be able to explain what `JSONB` is and how to use it to store and query JSON data efficiently.

Step 1: `JSONB` vs. `TEXT`

Feature	`TEXT`	`JSONB`
Storage	Stores the JSON data as a string.	Stores the JSON data in a decomposed binary format.
Performance	Slow to query, because the entire string has to be parsed each time.	Fast to query, because the data is already in a binary format.
Indexing	Can be indexed with a full-text search index.	Can be indexed with a GIN index, which is much more efficient.

Step 2: Choose the Right Tool for the Job

For our use case, we should use a JSONB column. This is because we need to be able to query the JSON data efficiently.

Step 3: Code Examples

Here’s how we can create a table with a JSONB column:

CREATE TABLE my_table (
    id SERIAL PRIMARY KEY,
    my_data JSONB
);

Here’s how we can insert some JSON data into the table:

INSERT INTO my_table (my_data) VALUES ('{"name": "John", "age": 30}');

Here’s how we can query the JSON data:

-- Get the value of the "name" key
SELECT my_data->>'name' FROM my_table;

-- Check if the "age" key is greater than 25
SELECT * FROM my_table WHERE (my_data->>'age')::int > 25;

-- Check if the data contains a certain key
SELECT * FROM my_table WHERE my_data ? 'name';

Systematic, production-ready debugging

Practice Question

You want to create an index on a `JSONB` column to speed up queries that use the `?` operator. Which type of index would you use?

Questions