Defining Models in PormG

PormG models describe the structure of your database tables using Julia code, inspired by Django ORM but tailored for Julia's syntax and performance.

What is a Model?

A model is a Julia type (usually a struct) that defines the fields (columns) and their types for a database table. Each model maps directly to a table in your PostgreSQL database.

Creating a Model

1. Edit Your Models File

   • By default, models are defined in db/models.jl.
   • Each model is a Julia struct using PormG field types.

2. Example Model Definition

Driver = Models.Model(
    id = Models.IDField(),
    name = Models.CharField(max_length=100),
    birthdate = Models.DateField(),
    nationality = Models.CharField(max_length=50)
)

1. Example of module contruction in db/models.jl

module models
import PormG.Models
import PormG.Models: RESTRICT, CASCADE, SET_NULL, SET_DEFAULT, DO_NOTHING


Status = Models.Model(
  statusId = Models.IDField(),
  status = Models.CharField()
)

Circuit = Models.Model( # You can create a model like a Django model for each table so that you can define a huge number of tables at once in just one file. Please capitalize the names of models.
  circuitId = Models.IDField(), # the PormG automatically do a lowercase for the name of the field, so you can use a capital letter in the name of the field, Hoewver you need to use a lowercase in the query operations.
  circuitRef = Models.CharField(),
  name = Models.CharField(),
  location = Models.CharField(),
  country = Models.CharField(),
  lat = Models.FloatField(),
  lng = Models.FloatField(),
  alt = Models.IntegerField(),
  url = Models.CharField()
)

Race = Models.Model(
  raceId = Models.IDField(),
  year = Models.IntegerField(),
  round = Models.IntegerField(),
  circuitId = Models.ForeignKey(Circuit, pk_field="circuitId", on_delete="CASCADE"),
  name = Models.CharField(),
  date = Models.DateField(),
  time = Models.TimeField(null=true),
  url = Models.CharField(),
  fp1_date = Models.DateField(null=true),
  fp1_time = Models.TimeField(null=true),
  fp2_date = Models.DateField(null=true),
  fp2_time = Models.TimeField(null=true),
  fp3_date = Models.DateField(null=true),
  fp3_time = Models.TimeField(null=true),
  quali_date = Models.DateField(null=true),
  quali_time = Models.TimeField(null=true),
  sprint_date = Models.DateField(null=true),
  sprint_time = Models.TimeField(null=true),
)

Driver = Models.Model(
  driverId = Models.IDField(),
  driverRef = Models.CharField(),
  number = Models.IntegerField(null=true),
  code = Models.CharField(),
  forename = Models.CharField(),
  surname = Models.CharField(),
  dob = Models.DateField(),
  nationality = Models.CharField(),
  url = Models.CharField()
)

Constructor = Models.Model(
  constructorId = Models.IDField(),
  constructorRef = Models.CharField(),
  name = Models.CharField(),
  nationality = Models.CharField(),
  url = Models.CharField()
)

Result = Models.Model(
  resultId = Models.IDField(),
  raceId = Models.ForeignKey(Race, pk_field="raceId", on_delete="CASCADE"),
  driverId = Models.ForeignKey(Driver, pk_field="driverId", on_delete="RESTRICT"),
  constructorId = Models.ForeignKey(Constructor, pk_field="constructorId", on_delete="RESTRICT"),
  number = Models.IntegerField(null=true),
  grid = Models.IntegerField(),
  position = Models.IntegerField(null=true),
  positionText = Models.CharField(),
  positionOrder = Models.IntegerField(),
  points = Models.FloatField(),
  laps = Models.IntegerField(),
  time = Models.CharField(null=true),
  milliseconds = Models.IntegerField(null=true),
  fastestLap = Models.IntegerField(null=true),
  rank = Models.IntegerField(null=true),
  fastestLapTime = Models.TimeField(null=true),
  fastestLapSpeed = Models.FloatField(null=true),
  statusId = Models.ForeignKey(Status, pk_field="statusId", on_delete="CASCADE")
)

Just_a_test_deletion = Models.Model(
  id = Models.IDField(),
  name = Models.CharField(),
  test_result = Models.ForeignKey(Result, pk_field="resultId", on_delete="CASCADE", null=true, related_name="test_deletion"),
  test_result2 = Models.ForeignKey(Result, pk_field="resultId", on_delete="CASCADE", null=true, related_name="test_deletion2")
)


Models.set_models(@__MODULE__, @__DIR__) # That is important to set the models in the module, otherwise it will not work, that need stay at the end of the file

end

• Each field uses a PormG field constructor (e.g., IDField, CharField, DateField).
• You can use keyword arguments to customize field options (e.g., max_length, unique, null).

Naming Conventions and Considerations

Model Naming Rules

• Use snake_case with capitalized first letter: User, Product, Order_item
• Use singular nouns: User not Users, Product not Products
• Be descriptive and clear: User_profile, Product_category, Order_history

Model Organization

• Keep models in db/models.jl or similar organized structure
• Group related models together in logical sections
• Use meaningful comments to explain complex relationships
• End with Models.set_models(@__MODULE__, @__DIR__) to register models

Supported Field Types

PormG provides comprehensive field types for all common database scenarios:

• Primary Key Fields: IDField, AutoField
• Text Fields: CharField, TextField, EmailField
• Numeric Fields: IntegerField, BigIntegerField, FloatField, DecimalField
• Date/Time Fields: DateField, DateTimeField, TimeField, DurationField
• Other Types: BooleanField, ImageField, BinaryField
• Relationship Fields: ForeignKey, OneToOneField

For detailed documentation on each field type, including parameters, examples, and best practices, see Field Types Reference.

For more details, see the PormG Documentation or the example scripts in the test/pg/ folder.