idb shim

Pure dart indexed db like API on top of native (Wasm compatible) or sembast implementation. Its goal is to support browsers that do not support the indexed_db api with very few changes as well as setting the base for a flutter implementation.

It also allows to test your database schema and access in vm unit tests.

• Project home page
• Project source code
• Samples (code and live demo)

Usage example:

• notepad_idb: Simple flutter notepad working on all platforms (web/mobile/desktop) (online demo)
• demo_idb: Simplest counter persistent app working on all platforms (web/mobile/desktop) (online demo)

Usage

Assume you have the existing:

import 'dart:indexed_db';
window.indexedDB.open(dbName, version: xxx, onUpgradeNeeded: yyy);

This can be replaced by:

import 'package:idb_shim/idb_browser.dart'
IdbFactory idbFactory = getIdbFactory();
idbFactory.open(dbName, version: xxx, onUpgradeNeeded: yyy);

All other existing code remains unchanged. Simple example below:

// define the store name
const String storeName = "records";

// open the database
Database db = await idbFactory.open("my_records.db", version: 1,
    onUpgradeNeeded: (VersionChangeEvent event) {
  Database db = event.database;
  // create the store
  db.createObjectStore(storeName, autoIncrement: true);
});

// put some data
var txn = db.transaction(storeName, "readwrite");
var store = txn.objectStore(storeName);
var key = await store.put({"some": "data"});
await txn.completed;

// read some data
txn = db.transaction(storeName, "readonly");
store = txn.objectStore(storeName);
Map value = await store.getObject(key);
await txn.completed;

Example

Simple notepad available here running on Flutter (iOS/Android/Web).

Flutter support

While idb_shim over sembast is a solution on Flutter, there is an implementation idb_sqflite based on sqflite for mobile (iOS and Android)

Testing

Testing with dartdevc

pub serve test --web-compiler=dartdevc --port=8079
pub run test -p chrome --pub-serve=8079

Known limitations/issues

Memory/Io implementation

• For autoincrement, if key is set, it cannot be set as a different type than int
• Nextunique and prevunique not supported (for now)
• No support for Cursor.source
• No generic support for blocked. It is always possible to upgrade the database, however other tabs will get blocked in their future calls
• Index.get: only by key is supported (no range yet)

Type of data

Supported types:

• Stuff that can be JSON serialized/deserialized (num, String, bool, null, List & Map)
• DateTime is supported as of 1.11
• Uint8List is supported as of 1.11
• null is no longer supported as a document value (although map field can be null though).

Limitations

• Cyclic dependecy are not supported (per JSON serialization)
• Large float are not converted to int (native indexeddb implementation does this)
• Don't create an index on boolean value. IndexedDB does not support that, however sembast implementation allows it (this could change). This will only be prevented in debug.

Type of key

• String and num (int or double) are supported for keys

Native exception

• Native exception type have no match in dart so a custom DatabaseError object is created to wrap the exception

Ie limitation

IE 11, Edge 12 has the following limitations:

• no support for reading objectStore.autoIncrement properties
• ObjectStore.count() without argument throw a 'DataError' exception...better avoid count() on IE...
• it seems ie close the transaction 'sooner' then chrome/firefox, i.e. calling an sync function that wrap an idb calls makes the transaction terminate
• IDBIndex.multiEntry not supported on ie

Safari limitation

Safari has the following limitations (as of v 9.0)

• no support for transactions on multiple stores
• very short transaction life cycle (no await on sdk 1.12)

Wasm

As of 2.4 the default implementation use js_interop which makes it wasm compatible if you import idb_shim.dart You can still use the legacy dart:html by importing idb_shim_client_native_html.dart.

Limitations:

• DateTime is converted manually to support DateTime (although not supported in Firefox)
• So for compatibility, data is jsified and dartified using custom encoder. To see if this could be removed in the future.

sdb

Experimental opinionated strong typed api based on idb database, which is currrently the main available options for locale storage on web with an easy support on desktop using sqlite. Basically the lowest common denominator. idb_shim only include a sembast based implementation (which is ok for testing but does not bring any good benefit, just use sembast directly as it works on all platforms).

Include idb_sqlite for a solid cross process safe io implementation.