Using EQL With ORMatic

ORMatic can translate high-level EQL expressions into SQLAlchemy select(…) statements.

• Build expressions over variables that carry the underlying Python type.

• Use krrood.ormatic.eql_interface.eql_to_sql() to get a translator you can evaluate against your session.

Example:

from sqlalchemy import create_engine
from sqlalchemy.orm import Session

from entity_query_language.entity import let
from entity_query_language import or_, in_

from dataset.example_classes import Position
from dataset.sqlalchemy_interface import Base, PositionDAO

from krrood.ormatic.eql_interface import eql_to_sql

engine = create_engine('sqlite:///:memory:')
session = Session(engine)
Base.metadata.create_all(engine)

# Insert sample data
session.add_all([
    PositionDAO.to_dao(Position(1, 2, 3)),
    PositionDAO.to_dao(Position(1, 2, 4)),
    PositionDAO.to_dao(Position(2, 9, 10)),
])
session.commit()

# Build an EQL expression
position = let(type_=Position)  # domain is irrelevant for translation
expr = position.z > 3

# Translate and execute
translator = eql_to_sql(expr, session)
rows = translator.evaluate()  # → PositionDAO rows with z > 3

# More complex logic
expr2 = or_(position.z == 4, position.x == 2)
translator2 = eql_to_sql(expr2, session)
rows2 = translator2.evaluate()

# Membership
expr3 = in_(position.x, [1, 7])
translator3 = eql_to_sql(expr3, session)
rows3 = translator3.evaluate()

Notes on the EQL translator:

• Variable resolution uses krrood.ormatic.dao.get_dao_class() to map EQL variables to DAO classes.

• Attribute comparisons on a single table are supported, including ==, !=, >, >=, <, <=, in, logical and/or, and not.

• If a variable’s DAO class cannot be found, a specific EQL translation error is raised to help diagnose missing mappings.

• EQL translation is not complete; feel free to extend it.