​​Using the JSON data type with MySQL 8 - Part II

by Edith Puclla

If you read - Using the JSON data type with MySQL 8 - Part I, you will see that inserting data into MySQL of JSON type is a very common and effective practice. Now we’ll see how to do it with a Python project, using SQLAlchemy and Docker Compose, which further automates this example. You can run this example using a single command: docker-compose up

Before getting down to work, we will review some important concepts:

  • Percona Server for MySQL is an open source, drop-in replacement for MySQL Community that provides better performance, more scalability, and enhanced security features.
  • SQLAlchemy is a library that allows us to communicate between Python programs and databases.
  • Docker Compose is a tool for defining and running multi-container Docker applications.

Let’s start with the structure of this project:

Project folder structure

We have a folder called app which contains the db.py file, and this is where we create the library database and establish the connection with this database.

db_user = os.environ['DB_USER']
db_password = os.environ['DB_PASSWORD']

engine = create_engine(f"mysql+pymysql://{db_user}:{db_password}@db:3306/library")

In this file, we also create the class transactions. This will create the fields for the library databases with SQLAlchemy; we define the attributes, and they will be the database fields. We have four attributes: book_id, tittle, publishes, and labels. The last one (labels) of JSON data type.

class transactions(base):
   __tablename__ = 'book'

   book_id = Column(Integer, primary_key=True)
   title = Column(String(50))
   publisher = Column(String(50))
   labels = Column(JSON)

   def __init__(self, book_id, title, publisher, labels):
       self.book_id = book_id
       self.title = title
       self.publisher = publisher
       self.labels = labels


Now let’s review the Python script called insert.py, where we use the transactions class to insert data into the database.

import db
from sqlalchemy.orm import sessionmaker

Session = sessionmaker(bind=db.engine)
session = Session()

tr1 = db.transactions(1,'Green House', 'Joe Monter', '{"about" : {"gender": "action", "cool": true, "notes": "labeled"}}')


Now let’s explore the docker-compose.yaml file, we have two services, the db and the api

version: "3.8"
   build: .
   container_name: api
       condition: service_healthy
   image: percona/percona-server:8.0
   container_name: db
   restart: always
     MYSQL_USER: root
     MYSQL_DATABASE: library
     test: ["CMD", "mysqladmin", "ping", "-h", "localhost"]
     timeout: 20s
     retries: 10
     - my-db:/var/lib/mysql
     - "3306:3306"
     - "3306"

# Names for volume

The db service uses the Percona Server for MySQL image (percona/percona-server:8.0) for the database and has a healthcheck that allows you to confirm when the database is started and ready to receive requests. The api service depends on the db service to start. The api service will build a Dockerfile, it does a build of the Python applications (of db.py and insert.py), so in this way, we can insert data into the database when it is ready.

It’s time to see the example in action; let’s locate it inside the json-mysql project and run docker-compose ps -d

Once this is done, we can connect to the database and query the table without needing to go inside the container with the following command:

docker exec -i db mysql -uroot -proot <<< "use library;show tables;select \* from book;describe book;"

We can check the data types of our fields and the inserted data. You will also see the JSON data type “labels” data type.

book_id	title	publisher	labels
1	Green House	Joe Monter	"{\\"about\\" : {\\"gender\\": \\"action\\", \\"cool\\": true, \\"notes\\": \\"labeled\\"}}"
2	El camino	Daniil Zotl	"{\\"about\\" : {\\"gender\\": \\"documental\\", \\"cool\\": true, \\"notes\\": \\"labeled\\"}}"
3	London Bridge	Mario Mesa	"{\\"about\\" : {\\"gender\\": \\"drama\\", \\"cool\\": true, \\"notes\\": \\"labeled\\"}}"
Field	Type	Null	Key	Default	Extra
book_id	int	NO	PRI	NULL	auto_increment
title	varchar(50)	YES		NULL
publisher	varchar(50)	YES		NULL
labels	json	YES		NULL

Use “docker compose ps” to see your services running. In this case, we have the “db” service running, which is for the database, and we have “api” with the state “exited,” which means that the scripts to create the database and insert the data into the database “library” was created.

NAME                COMMAND                  SERVICE             STATUS              PORTS
api                 "/bin/sh -c 'bash -C…"   api                 exited (0)
db                  "/docker-entrypoint.…"   db                  running (healthy)>3306/tcp, 33060/tcp

It was an example of inserting JSON data into MySQL using SQLAlchemy in Python and docker-compose for deployment.

You can find the project on GitHub. If there is any other way to make it better happy to hear it so I can improve this project.

You can explore more about Percona Server for MySQL, and if you want to see how this project start check Using the JSON data type with MySQL 8 - Part I

Edith Puclla

Edith Puclla is a Technology Evangelist of Percona Corporation, studied at 42 Silicon Valley School in California in 2020, and was part of the Outreachy Internship in 2021. She has a background in DevOps and is a Docker and Kubernetes enthusiast.

See all posts by Edith Puclla »


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