sqloquent 0.1.0

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Sqloquent

This is a SQL library with included bindings for sqlite. Inspired by Laravel and in particular Eloquent.

Overview

This package provides a set of interfaces and classes to make using a SQL database easier and simpler. (See section below for full list.)

The primary features are the SqlQueryBuilder and SqlModel base classes. The SqlQueryBuilder uses a monad pattern to build a query from various clauses. The SqlModel handles encoding, persisting, reading, and decoding models that correspond to rows. See below for the methods for each class.

These base classes can be coupled to the supplied sqlite3 coupling or to any SQL database client. See the "Usage" section below for detailed instructions.

Additionally, three classes, DeletedModel, HashedModel, and Attachment have been supplied to allow easy implementation of a system that includes a cryptographic audit trail. DeletedModel corresponds to any deleted model from a class that extends HashedModel and includes a restore method that can restore the deleted record.

There is an included CLI tool that generates code scaffolding for models and migrations, as well as track, apply, rollback, and refresh migrations.

Status

• Base interfaces
• Base test suite
• Base classes
• ORM
• Cryptographic bonus code
• Detailed query builder
• Code scaffold tools + CLI
• Schema migration system
• Decent documentation
• Add support for all SQL types in migration system.

Currently, only the basic sqlite3 types (affinities) of text, blob, integer, real, and numeric are supported by the migration system.

Setup and Usage

Requires Python 3.10+. Has not been tested with older Python versions.

Setup

pip install sqloquent

Usage

There are two primary ways to use this package: either with the bundled sqlite3 coupling or with a custom coupling to an arbitrary SQL database client. The cryptographic audit trail features can be used with any SQL database coupling.

Example

The most thorough example is the integration test. The model files can be found here, and the test itself is here.

The models were scaffolded using the CLI tool, then the details filled out in each. The relations were set up in the __init__.py file. The integration test generates migrations from these classes using the CLI tool, automigrates using the CLI tool, then does inserts/updates/deletes and checks the db for correctness. (These files provide a basic schema for correspondent banking.)

CLI Tool

For ease of development, a CLI tool is included which can be used for generating code scaffolds/boilerplates and for managing migrations. After installing via pip, run sqloquent in the terminal to view the help text.

The CLI tool can generate models and migrations, including the ability to generate migrations from completed models. Migrations can be handled manually or using an automatic method that tracks migrations via a migrations table. To use the migration tools, the environment variable CONNECTION_STRING must be set either in the CLI environment or in a .env file, e.g. CONNECTION_STRING=path/to/file.db. To insert this connection string into generated scaffold code, also define a MAKE_WITH_CONNSTRING environment variable and set it to anythong other than "false" or "0"; this is a convenience feature for working with sqlite3, since that is the only bundled coupling, but overwriting the file_path attribute on models at the app execution entry point is probably a better strategy -- if using another SQL binding, the connection info should be injected into the context manager (see section about binding to other SQL databases/engines below).

Additionally, the functionality of the CLI tool can be accessed programmatically through sqloquent.tools.

Note About Table Construction

The package as it stands relies upon text or varchar type id columns. The SqlModel uses a hexadecimal uuid4 as a GUID, while the HashedModel uses the sha256 of the deterministically encoded record content as a GUID. This can be changed for use with autoincrementing int id columns by extending SqlModel or SqliteModel and overriding the insert and insert_many methods to prevent setting the id via cls.generate_id(). However, this is not recommended unless the autoincrement id can be reliably discerned from the db cursor and there are no concerns about, say, synchronizing between instances using a CRDT.

Use one of the variants of the sqloquent make migration command to create a migration scaffold, then edit the result as necessary. If you specify the --model name path/to/model/file variant, the resultant source will include a unique index on the id column and simple indices on all other columns. This will also parse any class annotations that map to names of columns. For example, given the following class,

from sqloquent import SqlModel
class Thing(SqlModel):
    table = 'things'
    columns = ('id', 'name', 'amount')
    id: str
    name: str
    amount: int|None

the make migration --model command will produce the following migration:

from sqloquent import Migration, Table


def create_table_things() -> list[Table]:
    t = Table.create('things')
    t.text('id').unique()
    t.text('name').index()
    t.integer('amount').nullable().index()
    ...
    return [t]

def drop_table_things() -> list[Table]:
    return [Table.drop('things')]

def migration(connection_string: str = 'temp.db') -> Migration:
    migration = Migration(connection_string)
    migration.up(create_table_things)
    migration.down(drop_table_things)
    return migration

This should provide a decent scaffold for migrations, allowing the user of this package to model their data first as classes if desired. If some custom SQL is necessary, it can be added using a callback:

def add_custom_sql(clauses: list[str]) -> list[str]:
    clauses.append("do something sql-y")
    return clauses

def create_table_things() -> list[Table]:
    t = Table.create('things')
    t.text('id').unique()
    t.text('name').index()
    t.integer('amount').nullable().index()
    t.custom(add_custom_sql)
    ...
    return [t]

Examine the generated SQL of any migration using the sqloquent examine path/to/migration/file command.

Using the sqlite3 coupling

To use the supplied sqlite3 coupling without the cryptographic features, extend the SqliteModel, filling these attributes as shown below:

• table: str: the name of the table
• columns: tuple: the ordered tuple of column names

Additionally, set up any relevant relations using the ORM helper methods.

from sqloquent import SqliteModel, has_many, belongs_to


class ModelA(SqliteModel):
    table: str = 'model_a'
    columns: tuple = ('id', 'name', 'details')
    _details: dict = None

    def details(self, reload: bool = False) -> dict:
        """Decode json str to dict."""
        if self._details is None or reload:
            self._details = json.loads(self.data['details'])
        return self._details

    def set_details(self, details: dict = {}) -> ModelA:
        """Sets details and encodes to json str."""
        if details:
            self._details = details
        self.data['details'] = json.dumps(self._details)
        return self

class ModelB(SqliteModel):
    table: str = 'model_b'
    columns: tuple = ('id', 'name', 'model_a_id', 'number')


ModelA.model_b = has_many(ModelA, ModelB, 'model_a_id')
ModelB.model_a = belongs_to(ModelB, ModelA, 'model_a_id', True)

If you do not want to use the bundled ORM system, set up any relevant relations with _{related_name}: RelatedModel attributes and {related_name}(self, reload: bool = False) methods. Dicts should be encoded using json.dumps and stored in text columns. More flexibility can be gained at the expense of performance by using the packify package, e.g. to encode sets or classes that implement the packify.Packable interface.

from sqloquent import SqliteModel


class ModelA(SqliteModel):
    table: str = 'model_a'
    columns: tuple = ('id', 'name', 'details')
    _model_b: ModelB = None
    _details: dict = None

    def model_b(self, reload: bool = False) -> list[ModelB]:
        """The related model."""
        if self._model_b is None or reload:
            self._model_b = ModelB.query({'model_a_id': self.data['id']}).get()
        return self._model_b

    def set_model_b(self, model_b: ModelB) -> ModelA:
        """Helper method to save some lines."""
        model_b.data['model_a_id'] = self.data['id']
        model_b._model_a = self
        model_b.save()
        self._model_b = model_b
        return self

    def details(self, reload: bool = False) -> dict:
        """Decode json str to dict."""
        if self._details is None or reload:
            self._details = json.loads(self.data['details'])
        return self._details

    def set_details(self, details: dict = {}) -> ModelA:
        """Sets details and encodes to json str."""
        if details:
            self._details = details
        self.data['details'] = json.dumps(self._details)
        return self

class ModelB(SqliteModel):
    table: str = 'model_b'
    columns: tuple = ('id', 'name', 'model_a_id', 'number')
    _model_a: ModelA = None

    def model_a(self, reload: bool = False) -> Optional[ModelA]:
        """Return the related model."""
        if self._model_a is None or reload:
            self._model_a = ModelA.find(self.data['model_a_id'])
        return self._model_a

    def set_model_a(self, model_a: ModelA) -> ModelB:
        """Helper method to save some lines."""
        self.data['model_a_id'] = model_a.data['id']
        self._model_a = model_a
        model_a._model_b = self
        return self.save()

Coupling to a SQL Database Client

To couple to a SQL database client, complete the following steps.

0. Implement the CursorProtocol

If the database client does not include a cursor that implements the CursorProtocol, one must be implemented. Besides the methods execute, executemany, executescript, fetchone, and fetchall, an int rowcount attribute should be available and updated after calling execute.

If a rowcount attribute is not available, then the following methods of the base SqlQueryBuilder will need to be overridden in step 2:

• insert_many: returns the number of rows inserted
• update: returns the number of rows updated
• delete: returns the number of rows deleted

1. Implement the DBContextProtocol

See the SqliteContext class for an example of how to implement this interface. This is a standard context manager that accepts a class that implements ModelProtocol and returns an instance of the class made in step 0 when used with the following syntax:

with SomeDBContextImplementation(SomeModel) as cursor:
    cursor.execute('...')

Note that the connection information should be injected here in the context manager. The bundled sqlite bindings put the file path to the sqlite db on the models themselves to avoid having to rewrite and rebind the whole system to customize the db file path.

2. Extend SqlQueryBuilder

Extend SqlQueryBuilder and supply the class from step 1 as the second parameter to super().__init__(). Example:

class SomeDBQueryBuilder(SqlQueryBuilder):
    def __init__(self, model: type, *args, **kwargs) -> None:
        super().__init__(model, SomeDBContext, *args, **kwargs)

Additionally, since the SqlQueryBuilder was modeled on sqlite3, any difference in the SQL implementation of the database or db client will need to be reflected by overriding the relevant method(s).

3. Extend SqlModel

Extend SqlModel to include whatever class or instance information is required and inject the class from step 2 into self.query_builder_class in the __init__ method. Example:

from sqloquent import QueryBuilderProtocol, SqlModel


class SomeDBModel(SqlModel):
    """Model for interacting with SomeDB database."""
    some_config_key: str = 'some_config_value'
    query_builder_class: QueryBuilderProtocol = SomeDBQueryBuilder

    def __init__(self, data: dict = {}) -> None:
        super().__init__(data)

4. Extend Class from Step 3

To create models, simply extend the class from step 3, filling these attributes:

• table: str: the name of the table
• columns: tuple: the ordered tuple of column names

Additionally, set up any relevant relations using the ORM functions or, if you don't want to use the ORM, with _{related_name}: RelatedModel attributes and {related_name}(self, reload: bool = False) methods. Dicts should be encoded to comply with the database client, e.g. by using json.dumps for databases that lack a native JSON data type or for clients that require encoding before making the query. See the above example for using the sqlite3 coupling.

5. QueryBuilder Features

A few quick notes about QueryBuilder implementations, including the bundled SqlQueryBuilder and SqliteQueryBuilder:

• Pagination is accomplished using the skip(number) and take(number) methods, or by directly setting the limit and offset attributes. The offset will only apply when limit is specified because that is how SQL works generally.
• For iterating over large data sets, the chunk(number) method returns a generator that yields subsets with length equal to the specified number.
• For debugging/learning purposes, the to_sql produces human-readable SQL.
• The execute_raw(sql) method executes raw SQL and returns a tuple of (int rowcount, Any results from fetchall).

Using the Cryptographic Features

If a cryptographic audit trail is desirable, use the following multiple inheritance + injection pattern to couple the supplied classes to the desired ModelProtocol implementation, or use the sqlite versions and change the file_path attribute.

from sqloquent import HashedSqliteModel, DeletedSqliteModel, AttachmentSqlite
import sqloquent

env_db_file_path = 'some_file.db'
HashedModel.file_path = env_db_file_path
DeletedModel.file_path = env_db_file_path
Attachment.file_path = env_db_file_path

To use them with some other SQL binding, change the context_manager_class

This must be done exactly once. The value supplied for file_path (or relevant configuration value for other database couplings) should be set with some environment configuration system, but here it is only poorly mocked.

Using the ORM

The ORM is comprised of 4 classes inheriting from Relation and implementing the RelationProtocol: HasOne, HasMany, BelongsTo, and BelongsToMany.

Each Relation child class instance has a method create_property that returns a property that can be set on a model class:

class User(SqlModel):
    ...

class Avatar(SqlModel):
    columns = ('id', 'url', 'user_id')

User_Avatar = HasOne('user_id', User, Avatar)
User_Avatar.inverse = BelongsTo('user_id', Post, User)
User_Avatar.inverse.inverse = User_Avatar
User.avatar = User_Avatar.create_propert()
Avatar.user = User_Avatar.inverse.create_property()

There are also four helper functions for setting up relations between models: has_one, has_many, belongs_to, and belongs_to_many. These simplify and are the intended way for setting up relation between models. Far friendlier way to use the ORM.

class User(SqlModel):
    @property
    def friends(self) -> list[User]:
        friends = []
        if hasattr(self.my_friends) and self.my_friends:
            friends += self.my_friends
        if hasattr(self.befriended_by) and self.befriended_by:
            friends += self.befriended_by
        return friends
    @friends.setter
    def friends(self, friends: list[User]) -> None:
        current_friends = []
        if hasattr(self.my_friends) and self.my_friends:
            current_friends += self.my_friends
        if hasattr(self.befriended_by) and self.befriended_by:
            current_friends += self.befriended_by

        new_friends = tuple(f for f in friends if f not in current_friends)
        if hasattr(self.my_friends):
            self.my_friends = self.my_friends + new_friends
        elif hasattr(self.befriended_by):
            self.befriended_by = self.befriended_by + new_friends

class Avatar(SqlModel):
    columns = ('id', 'url', 'user_id')

class Post(SqlModel):
    columns = ('id', 'content', 'user_id')

class Friendships(SqlModel):
    columns = ('id', 'user1_id', 'user2_id')

User.avatar = has_one(User, Avatar)
User.posts = has_many(User, Post)
Post.author = belongs_to(Post, User)
User.my_friends = belongs_to_many(User, User, Friendships, 'user1_id', 'user2_id')
User.befriended_by = belongs_to_many(User, User, Friendships, 'user2_id', 'user1_id')

NB: polymorphic relations are not supported. See the Attachment class for an example of how to implement polymorphism if necessary. The above example also shows a contrived and probably suboptimal way to have a many-to-many relation on a single model.

Interfaces and Classes

Below is a list of interfaces, classes, errors, and functions. See the dox.md file generated by autodox for full documentation, or read interfaces.md for documentation on just the interfaces.

Interfaces

• CursorProtocol(Protocol)
• DBContextProtocol(Protocol)
• ModelProtocol(Protocol)
• JoinedModelProtocol(Protocol)
• RowProtocol(Protocol)
• QueryBuilderProtocol(Protocol)
• RelationProtocol(Protocol)
• ColumnProtocol(Protocol)
• TableProtocol(Protocol)
• MigrationProtocol(Protocol)

Classes

Classes implement the protocols or extend the classes indicated.

• SqlModel(ModelProtocol)
• SqlQueryBuilder(QueryBuilderProtocol)
• SqliteContext(DBContextProtocol)
• SqliteModel(SqlModel)
• SqliteQueryBuilder(SqlQueryBuilder)
• DeletedModel(SqlModel)
• DeletedSqliteModel(DeletedModel, SqliteModel)
• HashedModel(SqlModel)
• HashedSqliteModel(HashedModel, SqliteModel)
• Attachment(HashedModel)
• AttachmentSqlite(HashedSqliteModel)
• Row(RowProtocol)
• JoinedModel(JoinedModelProtocol)
• JoinSpec
• Relation(RelationProtocol)
• HasOne(Relation)
• HasMany(HasOne)
• BelongsTo(HasOne)
• BelongsToMany(Relation)
• Column(ColumnProtocol)
• Table(TableProtocol)
• Migration(MigrationProtocol)

Functions

The package includes some ORM helper functions for setting up relations and some other useful functions.

• dynamic_sqlite_model
• has_one
• has_many
• belongs_to
• belongs_to_many
• get_index_name

Tests

Open a terminal in the root directory and run the following:

python tests/test_classes.py
python tests/test_relations.py
python tests/test_migration.py
python tests/test_tools.py
python tests/test_integration.py

The tests demonstrate the intended (and actual) behavior of the classes, as well as some contrived examples of how they are used. Perusing the tests will be informative to anyone seeking to use/break this package, especially the integration test which demonstrates the full package. There are currently 194 unit tests + 1 e2e integration test.

ISC License

Copyleft (c) 2023 k98kurz

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyleft notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.