Support delete statements in batches

Closes #325

moor/CHANGELOG.md

@@ -13,6 +13,7 @@
   To create them in `onUpgrade`, use the new `createIndex` and `createTrigger` functions on a `Migrator`.
 - Support for moor-file queries that run on initialization ([#280](https://github.com/simolus3/moor/issues/280))
   Declare them like this `@create: INSERT INTO users VALUES ('default', 'user')`
+- Support deletes in batches ([#325](https://github.com/simolus3/moor/issues/325))
   
 ## 2.2.0
 

moor/lib/src/runtime/api/batch.dart

@@ -94,6 +94,16 @@ class Batch {
     }
   }
 
+  /// Deletes all rows from [table] matching the provided [filter].
+  ///
+  /// See also:
+  ///  - [QueryEngine.delete]
+  void delete<T extends Table, D extends DataClass>(TableInfo<T, D> table,
+      Expression<bool, BoolType> Function(T tbl) filter) {
+    final stmt = DeleteStatement(_engine, table)..where(filter);
+    _addContext(stmt.constructQuery());
+  }
+
   void _addContext(GenerationContext ctx) {
     final sql = ctx.sql;
     final variableSet = _createdStatements.putIfAbsent(sql, () => []);

moor/test/batch_test.dart

@@ -37,6 +37,8 @@ void main() {
         CategoriesCompanion(id: Value(1), description: Value('new1')),
         CategoriesCompanion(id: Value(2), description: Value('new2')),
       ]);
+
+      b.delete(db.categories, (_) => const Constant(true));
     });
 
     final transaction = executor.transactions;
@@ -67,6 +69,10 @@ void main() {
           ['new2', 2],
         ],
       ),
+      BatchedStatement(
+        'DELETE FROM categories WHERE 1;',
+        [[]],
+      ),
     ]));
   });