Provide information about the sql dialect at runtime

extras/mysql/README.md

@@ -20,7 +20,7 @@ You'll need to import `package:moor_mysql/moor_mysql.dart`.
 ## Limitations
 We're currently experimenting with other database engines - Moor was mainly designed for
 sqlite and supporting advanced features of MySQL is not a priority right now.
-- No migrations
+- No migrations - you'll need to create your tables manually
 - Some statements don't work
 - Compiled custom queries don't work - we can only parse sqlite. Of course, runtime custom
 queries with `customSelect` and `customUpdate` will work as expected.

extras/mysql/lib/moor_mysql.dart

@@ -71,6 +71,9 @@ class _MySqlDelegate extends DatabaseDelegate with _MySqlExecutor {
   @override
   TransactionDelegate get transactionDelegate => _TransactionOpener(this);
 
+  @override
+  SqlDialect get dialect => SqlDialect.mysql;
+
   @override
   Future<void> open([GeneratedDatabase db]) async {
     _connection = await MySqlConnection.connect(_settings);

moor/CHANGELOG.md

@@ -4,7 +4,7 @@ for details on how to use this feature.
 - New `backends` api, making it easier to write database drivers that work with moor. Apart from
 `moor_flutter`, new experimental backends can be checked out from git:
   1. `encrypted_moor`: An encrypted moor database: https://github.com/simolus3/moor/tree/develop/extras/encryption
-
+  2. `moor_mysql`: Work in progress mysql backend for moor. https://github.com/simolus3/moor/tree/develop/extras/mysql
 ## 1.6.0
 - Experimental web support! See [the documentation](https://moor.simonbinder.eu/web) for details.
 - Make transactions easier to use: Thanks to some Dart async magic, you no longer need to run

moor/lib/backends.dart

@@ -2,6 +2,7 @@
 /// with moor.
 library backends;
 
+export 'src/runtime/components/component.dart' show SqlDialect;
 export 'src/runtime/executor/executor.dart';
 export 'src/runtime/executor/helpers/delegates.dart';
 export 'src/runtime/executor/helpers/engines.dart';

moor/lib/src/runtime/components/component.dart

@@ -10,6 +10,11 @@ abstract class Component {
   void writeInto(GenerationContext context);
 }
 
+/// An enumeration of database systems supported by moor. Only
+/// [SqlDialect.sqlite] is officially supported, all others are in an
+/// experimental state at the moment.
+enum SqlDialect { sqlite, mysql }
+
 /// Contains information about a query while it's being constructed.
 class GenerationContext {
   /// Whether the query obtained by this context operates on multiple tables.
@@ -19,6 +24,7 @@ class GenerationContext {
   bool hasMultipleTables = false;
 
   final SqlTypeSystem typeSystem;
+  final SqlDialect dialect;
   final QueryExecutor executor;
 
   final List<dynamic> _boundVariables = [];
@@ -32,9 +38,11 @@ class GenerationContext {
 
   GenerationContext.fromDb(QueryEngine database)
       : typeSystem = database.typeSystem,
-        executor = database.executor;
+        executor = database.executor,
+        dialect = database.executor.dialect;
 
-  GenerationContext(this.typeSystem, this.executor);
+  GenerationContext(this.typeSystem, this.executor,
+      {this.dialect = SqlDialect.sqlite});
 
   /// Introduces a variable that will be sent to the database engine. Whenever
   /// this method is called, a question mark should be added to the [buffer] so

moor/lib/src/runtime/executor/executor.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:collection/collection.dart';
+import 'package:moor/src/runtime/components/component.dart';
 import 'package:moor/src/runtime/database.dart';
 import 'package:moor/src/utils/hash.dart';
 
@@ -8,11 +9,17 @@ import 'package:moor/src/utils/hash.dart';
 /// return their results in a raw form.
 ///
 /// This is an internal api of moor, which can break often. If you want to
-/// implement custom database backends, consider using a delegate as described
-/// [here](https://moor.simonbinder.eu/custom_backend)
+/// implement custom database backends, consider using the new `backends` API.
+/// The [moor_flutter implementation](https://github.com/simolus3/moor/blob/develop/moor_flutter/lib/moor_flutter.dart)
+/// might be useful as a reference. If you want to write your own database
+/// engine to use with moor and run into issues, please consider creating an
+/// issue.
 abstract class QueryExecutor {
   GeneratedDatabase databaseInfo;
 
+  /// The [SqlDialect] to use for this database engine.
+  SqlDialect get dialect => SqlDialect.sqlite;
+
   /// Performs the async [fn] after this executor is ready, or directly if it's
   /// already ready.
   Future<T> doWhenOpened<T>(FutureOr<T> fn(QueryExecutor e)) {

moor/lib/src/runtime/executor/helpers/delegates.dart

@@ -1,5 +1,6 @@
 import 'dart:typed_data' show Uint8List;
 import 'package:moor/moor.dart';
+import 'package:moor/src/runtime/components/component.dart';
 import 'package:moor/src/runtime/executor/helpers/results.dart';
 
 /// An interface that supports sending database queries. Used as a backend for
@@ -48,6 +49,9 @@ abstract class DatabaseDelegate implements QueryDelegate {
   Future<void> close() async {
     // default no-op implementation
   }
+
+  /// The [SqlDialect] understood by this database engine.
+  SqlDialect get dialect => SqlDialect.sqlite;
 }
 
 /// An interface which can execute sql statements.

moor/lib/src/runtime/executor/helpers/engines.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:moor/moor.dart';
+import 'package:moor/src/runtime/components/component.dart';
 import 'package:pedantic/pedantic.dart';
 import 'package:synchronized/synchronized.dart';
 
@@ -204,6 +205,8 @@ class _BeforeOpeningExecutor extends QueryExecutor
   }
 }
 
+/// A database engine (implements [QueryExecutor]) that delegated the relevant
+/// work to a [DatabaseDelegate].
 class DelegatedDatabase extends QueryExecutor with _ExecutorWithQueryDelegate {
   final DatabaseDelegate delegate;
   Completer<bool> _openingCompleter;
@@ -216,6 +219,9 @@ class DelegatedDatabase extends QueryExecutor with _ExecutorWithQueryDelegate {
   @override
   QueryDelegate get impl => delegate;
 
+  @override
+  SqlDialect get dialect => delegate.dialect;
+
   DelegatedDatabase(this.delegate,
       {this.logStatements, this.isSequential = false}) {
     // not using default value because it's commonly set to null

moor/lib/src/runtime/structure/columns.dart

@@ -193,7 +193,17 @@ class GeneratedIntColumn extends GeneratedColumn<int, IntType>
   void writeColumnDefinition(GenerationContext into) {
     // todo make this work with custom constraints, default values, etc.
     if (hasAutoIncrement) {
-      into.buffer.write('${$name} $typeName PRIMARY KEY AUTOINCREMENT');
+      String autoIncrementKeyword;
+      switch (into.dialect) {
+        case SqlDialect.sqlite:
+          autoIncrementKeyword = 'AUTOINCREMENT';
+          break;
+        case SqlDialect.mysql:
+          autoIncrementKeyword = 'AUTO INCREMENT';
+          break;
+      }
+
+      into.buffer.write('${$name} $typeName PRIMARY $autoIncrementKeyword');
     } else {
       super.writeColumnDefinition(into);
     }