Python ORM example application

This SQLAlchemy ORM example, running on Python, implements a basic REST API server for an e-commerce application scenario. Database access in this application is managed through SQL Alchemy ORM.

The source for this application can be found in the python/sqlalchemy directory of Yugabyte's Using ORMs with YugabyteDB GitHub repository.

Prerequisites

This tutorial assumes that you have:

YugabyteDB up and running. Download and install YugabyteDB by following the steps in Quick start.
Python 3 is installed
the Python packages (dependencies) : SQLAlchemy (SQLAlchemy), psycopg2 (psycopg2-binary) and JSONpickle (jsonpickle) installed:

To install these three packages, run the following command:
```
$ pip3 install psycopg2-binary sqlalchemy jsonpickle
```

Clone the "orm-examples" repository

Clone the Yugabyte orm-examples repository by running the following command.


$ git clone https://github.com/YugabyteDB-Samples/orm-examples.git

Set up the database connection

Update the database settings in the src/config.py file to match the following. If YSQL authentication is enabled, add the password (default for the yugabyte user is yugabyte).


import logging

listen_port = 8080
db_user = 'yugabyte'
db_password = 'yugabyte'
database = 'ysql_sqlalchemy'
schema = 'ysql_sqlalchemy'
db_host = 'localhost'
db_port = 5433

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s:%(levelname)s:%(message)s"
    )

Start the REST API server

Run the following Python script to start the server.


python3 ./src/rest-service.py

The REST API server will start and listen for your requests at http://localhost:8080.

Send requests to the application

Create 2 users.


$ curl --data '{ "firstName" : "John", "lastName" : "Smith", "email" : "jsmith@example.com" }' \
   -v -X POST -H 'Content-Type:application/json' http://localhost:8080/users


$ curl --data '{ "firstName" : "Tom", "lastName" : "Stewart", "email" : "tstewart@example.com" }' \
   -v -X POST -H 'Content-Type:application/json' http://localhost:8080/users

Create 2 products.


$ curl \
  --data '{ "productName": "Notebook", "description": "200 page notebook", "price": 7.50 }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/products


$ curl \
  --data '{ "productName": "Pencil", "description": "Mechanical pencil", "price": 2.50 }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/products

Create 2 orders.


$ curl \
  --data '{ "userId": "2", "products": [ { "productId": 1, "units": 2 } ] }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders


$ curl \
  --data '{ "userId": "2", "products": [ { "productId": 1, "units": 2 }, { "productId": 2, "units": 4 } ] }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders

Query results

Using the YSQL shell


$ ./bin/ysqlsh

ysqlsh (15.2-YB-2.25.0.0-b0)
Type "help" for help.

yugabyte=#


yugabyte=# SELECT count(*) FROM users;

 count
-------
     2
(1 row)


yugabyte=# SELECT count(*) FROM products;

 count
-------
     2
(1 row)


yugabyte=# SELECT count(*) FROM orders;

 count
-------
     2
(1 row)

Using the REST API


$ curl http://localhost:8080/users


{
  "content": [
    {
      "userId": 2,
      "firstName": "Tom",
      "lastName": "Stewart",
      "email": "tstewart@example.com"
    },
    {
      "userId": 1,
      "firstName": "John",
      "lastName": "Smith",
      "email": "jsmith@example.com"
    }
  ],
  ...
}


$ curl http://localhost:8080/products


{
  "content": [
    {
      "productId": 2,
      "productName": "Pencil",
      "description": "Mechanical pencil",
      "price": 2.5
    },
    {
      "productId": 1,
      "productName": "Notebook",
      "description": "200 page notebook",
      "price": 7.5
    }
  ],
  ...
}


$ curl http://localhost:8080/orders


{
  "content": [
    {
      "orderTime": "2019-05-10T04:26:54.590+0000",
      "orderId": "999ae272-f2f4-46a1-bede-5ab765bb27fe",
      "user": {
        "userId": 2,
        "firstName": "Tom",
        "lastName": "Stewart",
        "email": "tstewart@example.com"
      },
      "userId": null,
      "orderTotal": 25,
      "products": []
    },
    {
      "orderTime": "2019-05-10T04:26:48.074+0000",
      "orderId": "1598c8d4-1857-4725-a9ab-14deb089ab4e",
      "user": {
        "userId": 2,
        "firstName": "Tom",
        "lastName": "Stewart",
        "email": "tstewart@example.com"
      },
      "userId": null,
      "orderTotal": 15,
      "products": []
    }
  ],
  ...
}