sqflite

Description:

sqflite

sqflite #

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

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

Other platforms support:

Linux/Windows/DartVM support using sqflite_common_ffi
Experimental Web support using sqflite_common_ffi_web.

Usage example:

notepad_sqflite: Simple flutter notepad working on iOS/Android/Windows/linux/Mac

Getting Started #
To get started, you need to add sqflite to your project. Follow the steps below:


Open the terminal in your project root. You can do this by pressing Alt+F12 in Android Studio or Ctrl+` in VS Code.


Run the following command:


flutter pub add sqflite
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This command will add a line to your package's pubspec.yaml file and run an implicit flutter pub get. The added line will look like this:
dependencies:
sqflite:
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Usage example #
Import sqflite.dart
import 'package:sqflite/sqflite.dart';
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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/MacOS.
var db = await openDatabase('my_db.db');
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There is a basic migration mechanism to handle schema changes during 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();
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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();
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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, Object?> toMap() {
var map = <String, Object?>{
columnTitle: title,
columnDone: done == true ? 1 : 0
};
if (id != null) {
map[columnId] = id;
}
return map;
}

Todo();

Todo.fromMap(Map<String, Object?> 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();
}
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Read results #
Assuming the following read results:
List<Map<String, Object?>> records = await db.query('my_table');
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Resulting map items are read-only
// get the first record
Map<String, Object?> mapRead = records.first;
// Update it in memory...this will throw an exception
mapRead['my_column'] = 1;
// Crash... `mapRead` is read-only
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You need to create a new map if you want to modify it in memory:
// get the first record
Map<String, Object?> map = Map<String, Object?>.from(mapRead);
// Update it in memory now
map['my_column'] = 1;
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Transaction #
Don't use the database but only use the Transaction object in a transaction
to access the database. Keep in mind that the callbacks onCreate onUpgrade onDowngrade are already internally wrapped in a transaction, so there is no need to wrap your statements in a transaction within those callbacks.
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)');
});
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A transaction is committed if the callback does not throw an error. If an error is thrown,
the transaction is cancelled. So to rollback a transaction one way is to throw an exception.
Batch support #
To avoid ping-pong between 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();
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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);
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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();

// ...
});
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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 successfull operation is ran and committed even if one operation fails:
await batch.commit(continueOnError: true);
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Table and column names #
In general it is better to avoid using SQLite keywords for entity names. If any of the following
name 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"
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the helper will escape the name i.e.
db.query('table')
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will be equivalent to manually adding double-quote around the table name (confusingly here named table)
db.rawQuery('SELECT * FROM "table"');
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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']);
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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

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...

More #

How to guide
Notes about Desktop support
Notes about Encryption support
Notes about Web support