Add current_time_millis SQL function (#857)

docs/content/en/docs/Other engines/vm.md

@@ -133,6 +133,7 @@ For more details on sqlite compile options, see [their documentation](https://ww
   returns null. Otherwise, returns the result of applying the matching function in `dart:math`.
 - `regexp`: Wraps the Dart `RegExp` apis, so that `foo REGEXP bar` is equivalent to `RegExp(bar).hasMatch(foo)`. Note that we have to create a new
   `RegExp` instance for each `regexp` sql call, which can impact performance on large queries.
+- `current_time_millis`: Returns the current unix timestamp as milliseconds. Equivalent to `DateTime.now().millisecondsSinceEpoch` in Dart.
 
 Note that `NaN`, `-infinity` or `+infinity` are represented as `NULL` in sql.
 

moor/lib/src/ffi/moor_ffi_functions.dart

@@ -91,6 +91,13 @@ extension EnableMoorFunctions on Database {
       argumentCount: const AllowedArgumentCount(3),
       function: _containsImpl,
     );
+    createFunction(
+      functionName: 'current_time_millis',
+      deterministic: true,
+      directOnly: false,
+      argumentCount: const AllowedArgumentCount(0),
+      function: (List<dynamic> args) => DateTime.now().millisecondsSinceEpoch,
+    );
   }
 }
 

moor/test/ffi/moor_functions_test.dart

@@ -147,6 +147,11 @@ void main() {
       expect(selectSingle("moor_contains('hi', 'i', 1)"), 1);
     });
   });
+
+  test('current_time_millis', () {
+    final now = DateTime.now().millisecondsSinceEpoch;
+    expect(selectSingle('current_time_millis()'), closeTo(now, 100));
+  });
 }
 
 // utils to verify the sql functions behave exactly like the ones from the VM

moor_generator/lib/src/analyzer/moor/moor_ffi_extension.dart

@@ -23,7 +23,9 @@ class _MoorFfiFunctions with ArgumentCountLinter implements FunctionHandler {
   };
 
   @override
-  Set<String> get functionNames => const {'pow', ..._unaryFunctions};
+  Set<String> get functionNames {
+    return const {'pow', 'current_time_millis', ..._unaryFunctions};
+  }
 
   @override
   int argumentCountFor(String function) {
@@ -31,6 +33,8 @@ class _MoorFfiFunctions with ArgumentCountLinter implements FunctionHandler {
       return 1;
     } else if (function == 'pow') {
       return 2;
+    } else if (function == 'current_time_millis') {
+      return 0;
     }
     // ignore: avoid_returning_null
     return null;
@@ -46,6 +50,11 @@ class _MoorFfiFunctions with ArgumentCountLinter implements FunctionHandler {
   @override
   ResolveResult inferReturnType(AnalysisContext context, SqlInvocation call,
       List<Typeable> expandedArgs) {
+    if (call.name == 'current_time_millis') {
+      return const ResolveResult(
+          ResolvedType(type: BasicType.int, nullable: false));
+    }
+
     return const ResolveResult(
         ResolvedType(type: BasicType.real, nullable: true));
   }

moor_generator/test/analyzer/moor/moor_ffi_extension_test.dart

@@ -64,6 +64,15 @@ void main() {
     ]);
   });
 
+  test('infers return type for current_time_millis', () {
+    final result = engine.analyze('SELECT current_time_millis();');
+    final stmt = result.root as SelectStatement;
+
+    expect(stmt.resolvedColumns.map(result.typeOf), [
+      const ResolveResult(ResolvedType(type: BasicType.int, nullable: false))
+    ]);
+  });
+
   test('infers argument type', () {
     final result = engine.analyze('SELECT pow(2.5, ?);');
     final variable = result.root.allDescendants.whereType<Variable>().first;