DAO module

Quick Start

For a quick start and a high level description of the usage of this module, refer to Creating your DAO Class.

Module Documentation

Module for Data Access Objects implementation

nova_api.dao.camel_to_snake(name: str)

Converts a camel case name to snake case.

Parameters:name – String in camel case to be converted Returns:String in snake case

GenericDAO

class nova_api.dao.GenericDAO(table: str = None, fields: dict = None, return_class: Type[nova_api.entity.Entity] = <class 'nova_api.entity.Entity'>, prefix: str = None, **kwargs)

Interface class for the implementation of Data Access Objects.

__init__(table: str = None, fields: dict = None, return_class: Type[nova_api.entity.Entity] = <class 'nova_api.entity.Entity'>, prefix: str = None, **kwargs) → None

Initialize self. See help(type(self)) for accurate signature.

__weakref__

list of weak references to the object (if defined)

GenericSQLDAO

class nova_api.dao.generic_sql_dao.GenericSQLDAO(database_type: Type[nova_api.persistence.PersistenceHelper] = None, database_instance=None, table: str = None, fields: dict = None, return_class: Type[nova_api.entity.Entity] = <class 'nova_api.entity.Entity'>, prefix: str = None, **kwargs)

SQL implementation for the GenericDAO interface

__class__

alias of abc.ABCMeta

__delattr__

Implement delattr(self, name).

__dir__()

Default dir() implementation.

__eq__

Return self==value.

__format__()

Default object formatter.

__ge__

Return self>=value.

__getattribute__

Return getattr(self, name).

__gt__

Return self>value.

__hash__

Return hash(self).

__init__(database_type: Type[nova_api.persistence.PersistenceHelper] = None, database_instance=None, table: str = None, fields: dict = None, return_class: Type[nova_api.entity.Entity] = <class 'nova_api.entity.Entity'>, prefix: str = None, **kwargs) → None

Initialize self. See help(type(self)) for accurate signature.

__init_subclass__()

This method is called when a class is subclassed.

The default implementation does nothing. It may be overridden to extend subclasses.

__le__

Return self<=value.

__lt__

Return self<value.

__ne__

Return self!=value.

__new__()

Create and return a new object. See help(type) for accurate signature.

__reduce__()

Helper for pickle.

__reduce_ex__()

Helper for pickle.

__repr__

Return repr(self).

__setattr__

Implement setattr(self, name, value).

__sizeof__()

Size of object in memory, in bytes.

__str__

Return str(self).

__subclasshook__()

Abstract classes can override this to customize issubclass().

This is invoked early on by abc.ABCMeta.__subclasscheck__(). It should return True, False or NotImplemented. If it returns NotImplemented, the normal algorithm is used. Otherwise, it overrides the normal algorithm (and the outcome is cached).

__weakref__

list of weak references to the object (if defined)

close() → None

Closes the connection to the database

Returns:None

create(entity: nova_api.entity.Entity) → str

Creates a new row in the databse with data from entity.

Parameters:entity – The instance to save in the database. Returns:The entity uuid.

create_table_if_not_exists() → None

Creates the table in the database based on the return_class attributes. The types used in the database will be inferred through predict_db_types or through the field metadata in the “type” key.

Returns:None

generate_filters(filters: dict) -> (<class 'str'>, typing.List[str])

Converts a dict of filters to apply to a query to a SQL query format.

Example

>>> dao.generate_filters(
...     filters={"id_": "12345678901234567890123456789012",
...              "creation_datetime": [">", "2020-1-1"]})
("WHERE id_ = %s AND creation_datetime > %s",
["12345678901234567890123456789012", "2020-1-1"])

Raises:

• ValueError – If filters is None.
• TypeError – If filters is not a dict

Parameters:

filters – dictionary of filters to apply. The key must be a property of return_class and the value may be only the values, if equality is expected or a list with the comparator and the value.

Returns:

a tupĺe with the where statement and the list of params to use

get(id_: str) → Optional[nova_api.entity.Entity]

Recovers one entity with id_ from the database.

The id_ must be the nova_api generated id_ which is a 32-char uuid v4.

Raises:

• TypeError – If the UUID is not a string
• ValueError – If the UUID is not a valid UUID.

Parameters:

id – The UUID of the instance to recover

Returns:

None if no instance is found or a return_class instance if found

get_all(length: int = 20, offset: int = 0, filters: dict = None) -> (<class 'int'>, typing.List[nova_api.entity.Entity])

Recovers all instances that match the given filters up to the

length specified starting from the offset given.

The filters should be given as a dictionary, available keys are the return_class attributes. The values may be only the desired value or a list with the comparator in the first position and the value in the second.

Example

>>> dao.get_all(length=50, offset=0,
...             filters={"birthday":[">", "1/1/1998"],
...                      "name":"John"})
(2, [ent1, ent2])

Parameters:

• length – The number of items to select
• offset – The number of items to skip before starting to select
• filters – A dict with the filters to use. The key must be a valid attribute in the entity and the value may either be an specific value or a list with two elements: an operator and a value.

Returns:

A tuple with the totoal number of entities in the database and a list of the matched results.

remove(entity: nova_api.entity.Entity = None, filters: dict = None) → int

Removes entities from database. May be called either with an instance of return_class or a dict of filters. If both are passed, the instance will be removed and the filters won’t be considered.

Raises:

• RuntimeError – If entity is not a return_class instance and filters are None or if filters is not None and is not a dict.
• AssertionError – If the entity is not found in the database.
• NoRowsAffectedException – If no rows are affected by the delete query.

Parameters:

• entity – return_class instance to delete.
• filters – Filters to apply to delete query in dict format as specified by generate_filters

Returns:

Number of affected rows.

update(entity: nova_api.entity.Entity) → str

Updates an entity on the database.

Parameters:entity – The entity with updated values to update on the database. Returns:The id_ of the updated entity.