Database¶

Database classes provide persistence for Viper C++ documents using SQLite or remote connections.

When to use: Use Database for simple key-value persistence without history tracking. For the mutation DAG, see Commit Database.

Quick Start¶

>>> from dsviper import *
>>> MODEL = """
... namespace MyApp {8f14e45f-ceea-467a-9575-1c14b48f0b7e} {
...     concept User;
...     struct Profile { string city; uint16 age; };
...     attachment<User, Profile> profile;
... };
... """
>>> builder = DSMBuilder()
>>> builder.append("model.dsm", MODEL)
>>> report, dsm_defs, defs = builder.parse()
>>> report.has_error()
False
>>> defs.inject(globals())             # MY_APP_T_USER, MY_APP_A_USER_PROFILE, …
>>> key = ValueKey.create(MY_APP_T_USER, "0d2f0e1a-1111-4222-8333-444455556666")
>>> document = Value.create(MY_APP_S_PROFILE, {"city": "Paris", "age": 30})

A Database holds one state, with no history. Writes go in a transaction:

>>> db = Database.create_in_memory()
>>> db.extend_definitions(defs).count()
3
>>> db.begin_transaction()
>>> db.set(MY_APP_A_USER_PROFILE, key, document)
True
>>> db.commit()

get always returns a ValueOptional — never None. Ask is_nil() whether it holds anything, and unwrap() for the document:

>>> result = db.get(MY_APP_A_USER_PROFILE, key)
>>> result.is_nil()
False
>>> Value.dumps(result.unwrap())
{'city': 'Paris', 'age': 30}

>>> db.begin_transaction()
>>> db.delete(MY_APP_A_USER_PROFILE, key)
True
>>> db.commit()
>>> db.get(MY_APP_A_USER_PROFILE, key).is_nil()
True

Choosing the Right Class¶

Use Case	Class	Note
Simple CRUD, no history	`Database`	Creates `.vdb` files
Need version history	`CommitDatabase`	See Commit Database
Remote database access	`DatabaseRemote`	Client-server mode

Core Classes¶

`dsviper.Database`	A Database is a CRUD like transactional database.
`dsviper.DatabaseSQLite`	A low-level class used to represent a CRUD like database based on SQLite3 through the Databasing interface.
`dsviper.DatabaseRemote`	Accesses a CRUD like database on a remote repository, through the Databasing interface.
`dsviper.Databasing`	Abstracts the persistence layer behind a CRUD like database.

Low-Level¶

dsviper.SQLite

The settings and limits of one database file and of its SQLite3 build.