sql_crdt 1.1.1

Base package for Conflict-free Replicated Data Types (CRDTs) using SQL databases

Dart implementation of Conflict-free Replicated Data Types (CRDTs) using SQL databases.

This project is heavily influenced by James Long's talk CRTDs for Mortals and includes a Dart-native implementation of Hybrid Local Clocks (HLC) based on the paper Logical Physical Clocks and Consistent Snapshots in Globally Distributed Databases.

sql_crdt is based on the learnings from crdt, Libra, StoryArk and tudo.

This package contains the base functionality. Check sqlite_crdt and postgres_crdt for usable implementations.
See tudo for a real-world example.

⚠️ This package is still under development and may not be stable. The API may break at any time.

Notes

sql_crdt is not an ORM. The API is essentially that of a plain old SQL database with a few behavioural changes:

• Every table gets 3 columns automatically added: is_deleted, hlc, and modified
• Deleted records aren't actually removed but rather flagged in the is_deleted column
• Features a reactive watch method to subscribe to database queries
• Adds convenience methods getChangeset, watchChangeset and merge to simplify syncing with remote nodes

⚠ Because deleted records are only flagged as deleted, they may need to be sanitized in order to be compliant with GDPR and similar legislation.

API

The API is intentionally kept simple with a few methods:

• execute to run non-select SQL queries, e.g. inserts, updates, etc.
• query to perform a one-time query
• watch to receive query results whenever the database changes
• getChangeset to generate a serializable changeset of the local database
• watchChangeset a reactive alternative to get the changeset
• merge to apply a remote changeset to the local database
• transaction a blocking mechanism that avoids running simultaneous transactions in async code

Check the examples in sqlite_crdt and postgres_crdt for more details.

Features and bugs

Please file feature requests and bugs in the issue tracker.