Represents schema metadata for a relation.

This struct stores all extracted metadata about a relation including primary keys, foreign keys, field information, and indices. It serves as a central container for schema information used for automatic Ecto schema generation and query compilation.

Structure

• source - The database table name
• fields - List of field definitions with types and metadata
• primary_key - Primary key information
• foreign_keys - List of foreign key relationships
• indices - List of database indices

Access Behavior

The schema implements the Access behavior, allowing field lookup by name:

schema[:email]  # Returns the email field
schema[:id]     # Returns the id field

Usage with Relation Modules

Schemas are automatically created when you define a relation module and are accessible via the schema/0 function:

defmodule MyApp.Users do
  use Drops.Relation, repo: MyApp.Repo

  schema("users", infer: true)
end

# Access the relation's schema
schema = MyApp.Users.schema()

# Inspect schema metadata
schema.source        # => :users
schema.fields        # => [%Field{name: :id, type: :integer}, ...]
schema.primary_key   # => %PrimaryKey{fields: [:id]}

# Access specific fields
email_field = schema[:email]
id_field = schema[:id]

# Get field information
email_field.type     # => :string
email_field.meta     # => %{type: :varchar, ...}

Field Access Examples

# Check if a field exists
if schema[:email] do
  IO.puts("Email field exists with type: " <> to_string(schema[:email].type))
end

# Get all field names
field_names = Enum.map(schema.fields, & &1.name)
# => [:id, :name, :email, :active, :inserted_at, :updated_at]

# Filter fields by type
string_fields = Enum.filter(schema.fields, &(&1.type == :string))