The document discusses data storage options in Electron, particularly for building applications like Evernote, focusing on small datasets and various storage mechanisms, including local storage and IndexedDB. It highlights the benefits of using rxdb, an observable object store based on SQLite tailored for Electron, which supports live data updates and integrates seamlessly with application frameworks like Redux. Key features of rxdb include multi-window support, efficient querying, and being optimized for performance in managing large datasets.

1. Electron, Databases,
and RxDB
An overview of Electron data storage options,
and a new observable object store.
@bengotow

2. I want to build Evernote with Electron.
How should I store user’s data?

3. “Notes”
Recent Notes
Full-text Search Edit Note

4. • One user, their persistent filesystem
• For small datasets (<1,000 items), loading /
saving JSON and filtering it in memory is fine.
Do I need a database?

5. • Chrome has great key-value storage options,
and we can manually maintain indexes.
Do I need a relational
database?
KEY VALUE
A {“name”:”My first document..
B {“name”:”Another note…
C {“name”: “Favorite note…
RECENT_IDS [“B”, “C”]

6. LocalStorage
• Synchronous
• Strings only
• Retrieve keys
• <10MB (#8337)
Key Value Storage
IndexedDB
• Sync or async
• Strings, JSON
• Retrieve keys, ranges
• Indexed scan for key
• < 1/3 free disk space
Or use the Filesystem!

7. • But… I need full-text search
• But… I want to query and sort by arbitrary fields
• But… I want to support millions of notes
• But… I may need more than 1/3 of the available
disk space. (IndexedDB limit)
🤔

8. • De-facto standard for relational storage in client-
side applications (macOS, iOS, Android, etc.)
• Builds everywhere, no dependencies
• Simple, fast, reliable
• Open source, great documentation

9. SQLite + ORM

10. SQLite + ORM

11. But… for Electron?
• Most JavaScript database wrappers were built
for server-side NodeJS.
• Heavy focus on querying, connection pools,
etc., limited APIs for connecting models to
views.

12. • CoreData (iOS): NSFetchedResultsController
• YapDatabase (iOS): YapDatabaseView
• AndroidSQLite (Android): View “Cursors”
“Give me the notes matching this query, and let
me know if the results change.”

13. Electron-RxDB
• Observable object store built on SQLite:
CoreData for Electron
• Built to power the Nylas N1 mail client,
tuned for performance

14. Define a Note

15. Save a Note
Query for Notes

16. Create a Notes view

17. Create a Notes view

18. • Database is an EventEmitter, broadcasts events
when transactions are committed.
• Queries return RxJS Observables that emit new
result sets as transactions are committed.
• Optimizations prevent RxDB from re-running SQL
queries in common cases
SQLite 💖 RxJS

19. Nylas N1
• RxDB provides live “slices” of 1GB+ of mail data
• Views bind to Flux / Redux stores for application
state, RxDB queries for data.
• Many features (mail rules, notifications, etc.)
implemented with database listeners.

20. Built for Electron
• Multi-window support
• Always builds SQLite for Electron
• Example Electron app: “Notes”

21. Thanks!
bengotow/electron-RxDB
@bengotow