An overview of Electron data storage options (IndexedDB, LocalStorage, SQLite), and a new observable object store.

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