sql_crdt

Description:

sql crdt

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 crdt and the learnings from Libra, StoryArk and tudo.
This package is is abstract and implements the base functionality for CRDTs backed by a relational database. Check sqlite_crdt and postgres_crdt for usable implementations.
See also tudo for a real-world FOSS implementation.
This package is compatible with crdt_sync, a turnkey approach for real-time network synchronization of CRDT nodes.
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.
A reactive watch method to subscribe to database queries.
Convenience methods getChangeset and merge inherited from the crdt package to sync 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.
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.