SQLite plugin for Flutter

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5 years ago

sqflite

SQLite plugin for Flutter. Supports iOS, Android and MacOS.

Support transactions and batches
Automatic version management during open
Helpers for insert/query/update/delete queries
DB operation executed in a background thread on iOS and Android

Getting Started

In your flutter project add the dependency:

dependencies:
  ...
  sqflite: ^1.2.0

For help getting started with Flutter, view the online documentation.

Usage example

Import sqflite.dart

import 'package:sqflite/sqflite.dart';

Opening a database

A SQLite database is a file in the file system identified by a path. If relative, this path is relative to the path obtained by getDatabasesPath(), which is the default database directory on Android and the documents directory on iOS.

var db = await openDatabase('my_db.db');

There is a basic migration mechanism to handle schema changes during the opening.

Many applications use one database and would never need to close it (it will be closed when the application is terminated). If you want to release resources, you can close the database.

await db.close();

See more information on opening a database.
Full migration example

Raw SQL queries

Demo code to perform Raw SQL queries

// Get a location using getDatabasesPath
var databasesPath = await getDatabasesPath();
String path = join(databasesPath, 'demo.db');

// Delete the database
await deleteDatabase(path);

// open the database
Database database = await openDatabase(path, version: 1,
    onCreate: (Database db, int version) async {
  // When creating the db, create the table
  await db.execute(
      'CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)');
});

// Insert some records in a transaction
await database.transaction((txn) async {
  int id1 = await txn.rawInsert(
      'INSERT INTO Test(name, value, num) VALUES("some name", 1234, 456.789)');
  print('inserted1: $id1');
  int id2 = await txn.rawInsert(
      'INSERT INTO Test(name, value, num) VALUES(?, ?, ?)',
      ['another name', 12345678, 3.1416]);
  print('inserted2: $id2');
});

// Update some record
int count = await database.rawUpdate(
    'UPDATE Test SET name = ?, VALUE = ? WHERE name = ?',
    ['updated name', '9876', 'some name']);
print('updated: $count');

// Get the records
List<Map> list = await database.rawQuery('SELECT * FROM Test');
List<Map> expectedList = [
  {'name': 'updated name', 'id': 1, 'value': 9876, 'num': 456.789},
  {'name': 'another name', 'id': 2, 'value': 12345678, 'num': 3.1416}
];
print(list);
print(expectedList);
assert(const DeepCollectionEquality().equals(list, expectedList));

// Count the records
count = Sqflite
    .firstIntValue(await database.rawQuery('SELECT COUNT(*) FROM Test'));
assert(count == 2);

// Delete a record
count = await database
    .rawDelete('DELETE FROM Test WHERE name = ?', ['another name']);
assert(count == 1);

// Close the database
await database.close();

Basic information on SQL here.

SQL helpers

Example using the helpers

final String tableTodo = 'todo';
final String columnId = '_id';
final String columnTitle = 'title';
final String columnDone = 'done';

class Todo {
  int id;
  String title;
  bool done;

  Map<String, dynamic> toMap() {
    var map = <String, dynamic>{
      columnTitle: title,
      columnDone: done == true ? 1 : 0
    };
    if (id != null) {
      map[columnId] = id;
    }
    return map;
  }

  Todo();

  Todo.fromMap(Map<String, dynamic> map) {
    id = map[columnId];
    title = map[columnTitle];
    done = map[columnDone] == 1;
  }
}

class TodoProvider {
  Database db;

  Future open(String path) async {
    db = await openDatabase(path, version: 1,
        onCreate: (Database db, int version) async {
      await db.execute('''
create table $tableTodo ( 
  $columnId integer primary key autoincrement, 
  $columnTitle text not null,
  $columnDone integer not null)
''');
    });
  }

  Future<Todo> insert(Todo todo) async {
    todo.id = await db.insert(tableTodo, todo.toMap());
    return todo;
  }

  Future<Todo> getTodo(int id) async {
    List<Map> maps = await db.query(tableTodo,
        columns: [columnId, columnDone, columnTitle],
        where: '$columnId = ?',
        whereArgs: [id]);
    if (maps.length > 0) {
      return Todo.fromMap(maps.first);
    }
    return null;
  }

  Future<int> delete(int id) async {
    return await db.delete(tableTodo, where: '$columnId = ?', whereArgs: [id]);
  }

  Future<int> update(Todo todo) async {
    return await db.update(tableTodo, todo.toMap(),
        where: '$columnId = ?', whereArgs: [todo.id]);
  }

  Future close() async => db.close();
}

Read results

Assuming the following read results:

List<Map<String, dynamic>> records = await db.query('my_table');

Resulting map items are read-only

// get the first record
Map<String, dynamic> mapRead = records.first;
// Update it in memory...this will throw an exception
mapRead['my_column'] = 1;
// Crash... `mapRead` is read-only

You need to create a new map if you want to modify it in memory:

// get the first record
Map<String, dynamic> map = Map<String, dynamic>.from(mapRead);
// Update it in memory now
map['my_column'] = 1;

Transaction

Don’t use the database but only use the Transaction object in a transaction to access the database

await database.transaction((txn) async {
  // Ok
  await txn.execute('CREATE TABLE Test1 (id INTEGER PRIMARY KEY)');
  
  // DON'T  use the database object in a transaction
  // this will deadlock!
  await database.execute('CREATE TABLE Test2 (id INTEGER PRIMARY KEY)');
});

A transaction is committed if the callback does not throw an error. If an error is thrown, the transaction is canceled. So to rollback, a transaction one way is to throw an exception.

Batch support

To avoid ping-pong between the dart and native code, you can use Batch:

batch = db.batch();
batch.insert('Test', {'name': 'item'});
batch.update('Test', {'name': 'new_item'}, where: 'name = ?', whereArgs: ['item']);
batch.delete('Test', where: 'name = ?', whereArgs: ['item']);
results = await batch.commit();

Getting the result for each operation has a cost (id for insertion and number of changes for update and delete), especially on Android where an extra SQL request is executed. If you don’t care about the result and worry about performance in big batches, you can use

await batch.commit(noResult: true);

Warning, during a transaction, the batch won’t be committed until the transaction is committed

await database.transaction((txn) async {
  var batch = txn.batch();
  
  // ...
  
  // commit but the actual commit will happen when the transaction is committed
  // however the data is available in this transaction
  await batch.commit();
  
  //  ...
});

By default, a batch stops as soon as it encounters an error (which typically reverts the uncommitted changes). You can ignore errors so that every successful operation is run and committed even if one operation fails:

await batch.commit(continueOnError: true);

Table and column names

In general, it is better to avoid using SQLite keywords for entity names. If any of the following names is used:

"add","all","alter","and","as","autoincrement","between","case","check","collate","commit","constraint","create","default","deferrable","delete","distinct","drop","else","escape","except","exists","foreign","from","group","having","if","in","index","insert","intersect","into","is","isnull","join","limit","not","notnull","null","on","or","order","primary","references","select","set","table","then","to","transaction","union","unique","update","using","values","when","where"

the helper will escape the name i.e.

db.query('table')

will be equivalent to manually adding double-quote around the table name (confusingly here named table)

db.rawQuery('SELECT * FROM "table"');

However in any other raw statement (including orderBy, where, groupBy), make sure to escape the name properly using double quote. For example see below where the column name group is not escaped in the columns argument, but is escaped in the where argument.

db.query('table', columns: ['group'], where: '"group" = ?', whereArgs: ['my_group']);

Supported SQLite types

No validity check is done on values yet so please avoid non supported types https://www.sqlite.org/datatype3.html

DateTime is not a supported SQLite type. Personally I store them as int (millisSinceEpoch) or string (iso8601)

bool is not a supported SQLite type. Use INTEGER and 0 and 1 values.

More information on supported types here.

INTEGER

Dart type: int
Supported values: from -2^63 to 2^63 – 1

REAL

Dart type: num

TEXT

Dart type: String

BLOB

Dart type: Uint8List
Dart type List<int> is supported but not recommended (slow conversion)

Current issues

Due to the way transaction works in SQLite (threads), concurrent read and write transaction are not supported. All calls are currently synchronized and transactions block are exclusive. I thought that a basic way to support concurrent access is to open a database multiple times but it only works on iOS as Android reuses the same database object. I also thought a native thread could be a potential future solution however on android accessing the database in another thread is blocked while in a transaction…
Currently INTEGER are limited to -2^63 to 2^63 – 1 (although Android supports bigger ones)

How to guide

Installation:

Use this package as a library

1. Depend on it

Add this to your package’s pubspec.yaml file:


dependencies:
  sqflite: ^1.2.0

2. Install it

You can install packages from the command line:

with Flutter:


$ flutter pub get

Alternatively, your editor might support flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:


import 'package:sqflite/sqflite.dart';

Download SQLite flutter plugin on GitHub

https://github.com/tekartik/sqflite

Get more information about the SQLite Flutter plugin on Pub.Dev

https://pub.dev/packages/sqflite

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