Database

Viper provides two database types for persistence:

Type

Use Case

History

Database

Simple key-value storage

No

CommitDatabase

Versioned data

Yes (DAG)

This page covers the simple Database. For versioned storage, see CommitDatabase.

Creating a Database

>>> from dsviper import *

# Create in memory
>>> db = Database.create_in_memory()

# Create on disk
>>> db = Database.create("data.vdb")

# Open existing
>>> db = Database.open("data.vdb")

Setting Up Definitions

# Load definitions from DSM
>>> builder = DSMBuilder.assemble("model.dsm")
>>> report, dsm_defs, defs = builder.parse()

# Extend database with definitions
>>> db.extend_definitions(defs)
>>> defs.inject()

CRUD Operations

# Create
>>> key = TUTO_A_USER_LOGIN.create_key()
>>> login = TUTO_A_USER_LOGIN.create_document()
>>> login.nickname = "alice"

# Write (requires transaction)
>>> db.begin_transaction()
>>> db.set(TUTO_A_USER_LOGIN, key, login)
>>> db.commit()

# Read
>>> result = db.get(TUTO_A_USER_LOGIN, key)
>>> result.unwrap()
{nickname='alice', password=''}

# Update
>>> db.begin_transaction()
>>> login.password = "secret"
>>> db.set(TUTO_A_USER_LOGIN, key, login)
>>> db.commit()

# Delete
>>> db.begin_transaction()
>>> db.delete(TUTO_A_USER_LOGIN, key)
>>> db.commit()

# List all keys
>>> db.keys(TUTO_A_USER_LOGIN)
[key1, key2, ...]

Transactions

All write operations require a transaction:

>>> db.begin_transaction()
>>> # ... mutations ...
>>> db.commit()      # Apply changes

# Or rollback
>>> db.begin_transaction()
>>> # ... mutations ...
>>> db.rollback()    # Discard changes

Safe transaction pattern - Always use try/finally to ensure cleanup:

db.begin_transaction()
try:
    db.set(attachment, key, document)
    db.commit()
except ViperError:
    db.rollback()
    raise

Choosing Between Database and CommitDatabase

Feature

Database

CommitDatabase

Simple CRUD

✓

✓

History

✗

✓

Sync

✗

✓

Embedded definitions

✗

✓

Use case

Caches, temp storage

Application data

What’s Next