Persistency Implementation

[naman108]

Persistency requirements

• Support Create operation to add a node instance to the DB
• Support Delete operation to delete a node instance from the DB
• Support Read operation to query nodes from the DB
• Support Update operation to modify
• Support the Creation of new tables as new classes are added
• Support Modification of existing tables as classes are changed

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Persistency risks

• Interfere with existing applications of persistency
• increase latency

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Persistency milestones

• [x] merge main into persistene
• [x] Creation of tables as new classes are added
  • [x] check if the table exists every time the class is instantiated
  • [x] infer all table columns from the node attributes
  • [x] use sqlalchemy to instantiate new table
• [ ] Create operation to add node instance to the DB
  • [x] check if table exists every time a node is instantiate
  • [x] access the object id at instantiation
  • [ ] instantiate a database persistent object with the object id
• [ ] Read operation to access contents in the DB
  • [ ] add support for a static method in the persistency object which allows the passing of queries, in string form or as SQLAlchemy Queries *
  • [ ] instantiate node as return value without calling create or update operations
  • [ ] test all defined functionality
• [ ] Update operation to modify node instance in the DB
  • [ ] override all attribute setters to make sqlalchemy call to update the change in the db
    • asynchronously should this update be performed asynchronously ignoring a failed state or should it be done synchronously raising an exception in the event it was not updated
    • should this be done on every update or should there be a manual update command used to send changes to the db?
  • [ ] add auto type checking to validate that the passed types are correct? (unpythonic, enforcing strict typing)
• [ ] Modification of existing tables as classes are changed
  • [ ] check for differences between table columns and class attributes at class instantiation
  • [ ] if different, generate a table alter command (SQLAlchemy to my knowledge doesn't support altering tables in it's API
• [ ] Delete operation to delete a node instance from the DB
  • [ ] when delete magic method is called check if an object with the given object_id exists in the DB
  • [ ] if it does delete the object using sqlalchemy

[brothercorvo]

@naman108 how is that impacting the work we are doing with DigitalPi?

[naman108]

it would change the way that we handle generation as we wouldn't need to generate an sqlalchemy table class but this will take a lot of work so probably out of scope for now.

[brothercorvo]

@naman108 is this done with the new version of the DigitalPi

[naman108]

no it's not been touched, currently we use an alternative system of builders, directors and controllers to perform the mapping