logicbank 1.0.0

Declare multi-table rules for SQLAlchemy update logic -- 40X more concise, Python for extensibility.

This package enables you to declare rules that govern SQLAlchemy update transaction logic (multi-table derivations, constraints, and actions such as sending mail or messages).

Logic is stated in Python, and is over an 40X more concise than code.

Features

Logic is declared in Python (example below), and is:

• Extensible: logic consists of rules (see below), plus standard Python code

• Multi-table: rules like sum automate multi-table transactions

• Scalable: rules are pruned and optimized; for example, sums are processed as 1 row adjustment updates, rather than expensive SQL aggregate queries

• Manageable: develop and debug your rules in IDEs, manage it in SCS systems (such as git) using existing procedures

Example:

The following 5 rules represent the same logic as 200 lines of Python:

To activate the rules declared above:

LogicBank.activate(session=session, activator=declare_logic)

Depends on:

• SQLAlchemy

• Python 3.8

More information:

The github project includes documentation and examples.

Acknowledgements

Many thanks to

• Tyler Band, for testing and the Banking sample

• Max Tardiveau, for testing

• Nishanth Shyamsundar, for testing

• Achim Götz, for design collaboration

Change Log

0.0.6 - Initial Version

0.0.7 - Class Name can differ from Table Name

0.0.8 - Much-reduced pip-install dependencies

0.0.9 - Hybrid attribute support, old_row example

0.1.0 - Hybrid attribute support, bug fix

0.1.1 - Allocation example - allocate a payment to a set of outstanding orders

0.2.0 - Minor design refactoring of allocation

0.3.0 - Include logic_bank.extensions (allocation), constraint exceptions raised as ConstraintExceptions

0.4.0 - Eliminate “engine” from runtime, to facilitate use in servers. Rework nw tests to centralize open logic in setup().

0.5.0 - Support for Referential Integrity, with examples.

0.5.1 - Support domain object constructors with complex (side effects) __init__ behavior; use row_mapper.column_attrs (not all_orm_descriptors) to avoid ‘flush already in progress’ when using flask_sqlalchemy

0.6.0 - Support for

• Rule Extensibility

  • e.g., for auditing

• Generic early events: early_row_event_all_classes (see Rule Extensibility link above)

  • e.g., for time/date stamping

• New LogicRow functions (see Rule Extensibility link above):

  • are_attributes_changed

  • set_same_named_attributes

• Minor rename of logic class in nw. Some screen shots may still show the old name (rules_bank.py) instead of logic.py.

• Bug Fix: (normal) row events weren’t firing (other events - early and commit events - were fine)

0.7.0 - Custom Exceptions, Improved docstrings, samples (and Tutorial) reorganized into examples folder

0.8.0 - Custom Exceptions, callback signature changed to include additional parameters

0.9.0 - Add logicRow.get_derived_attributes, which can be used to enforce behaviors such as Unalterable Derivations

0.9.2 - Add session to logic_row.__str__(), listeners

0.9.3 - Allow for nulls in summed/sum

0.9.4 - Fix bad Warning: Missing Parent:

0.9.5 - Reduce requirement to initialize summed field

0.9.6 - Show Constraint Failures in Console Log