Sorting Database Objects by Distance from Target Coordinate

This code defines a function that sorts objects stored in a database based on their distance from a target coordinate, with the sorting criterion being the distance between the object's coordinates and the target coordinate.

Technology Stack : The code uses the SQLAlchemy-Utils library and SQLAlchemy ORM to interact with the database. It uses SQL functions to calculate distances and perform sorting.

Code Type : The type of code

Code Difficulty : Advanced

                
                    
def sort_objects_by_distance(session, object_table, coordinate_column, target_coordinate):
    """
    Sort objects in a table by their distance from a target coordinate.
    
    Args:
        session (Session): SQLAlchemy session object.
        object_table (Table): SQLAlchemy table object representing the objects.
        coordinate_column (str): The column name that stores the coordinates.
        target_coordinate (tuple): The target coordinate as (latitude, longitude).
    """
    from sqlalchemy import func
    from sqlalchemy.orm import aliased

    # Create an alias for the object table to use in the subquery
    object_alias = aliased(object_table)

    # Calculate the distance between the target coordinate and each object's coordinate
    distance_expr = func.sqrt(
        func.pow(object_alias[coordinate_column][0] - target_coordinate[0], 2) +
        func.pow(object_alias[coordinate_column][1] - target_coordinate[1], 2)
    )

    # Order the objects by their calculated distance from the target coordinate
    sorted_objects = session.query(object_alias).order_by(distance_expr).all()

    return sorted_objects