From 79aedea60eb160f0b6f3958209acf24eb0f9b758 Mon Sep 17 00:00:00 2001
From: YeungKC <I@YeungKC.com>
Date: Thu, 10 Mar 2022 21:36:02 +0800
Subject: [PATCH] Determine schema version. (#1743)

Avoid an unnecessary write to the database when no migration is needed.
---
 docs/lib/snippets/migrations/runtime_verification.dart | 2 +-
 drift/lib/src/runtime/executor/helpers/engines.dart    | 3 ++-
 drift/test/engines/delegated_database_test.dart        | 8 +++++++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/docs/lib/snippets/migrations/runtime_verification.dart b/docs/lib/snippets/migrations/runtime_verification.dart
index 500abcee..c29d9ce3 100644
--- a/docs/lib/snippets/migrations/runtime_verification.dart
+++ b/docs/lib/snippets/migrations/runtime_verification.dart
@@ -42,4 +42,4 @@ class MyDatabase extends _$MyDatabase {
         },
       );
 }
-// #enddocregion
\ No newline at end of file
+// #enddocregion
diff --git a/drift/lib/src/runtime/executor/helpers/engines.dart b/drift/lib/src/runtime/executor/helpers/engines.dart
index 3d842ae9..0fa766cc 100644
--- a/drift/lib/src/runtime/executor/helpers/engines.dart
+++ b/drift/lib/src/runtime/executor/helpers/engines.dart
@@ -334,7 +334,8 @@ class DelegatedDatabase extends _BaseExecutor {
     final openingDetails = OpeningDetails(oldVersion, currentVersion);
     await user.beforeOpen(_BeforeOpeningExecutor(this), openingDetails);
 
-    if (versionDelegate is DynamicVersionDelegate) {
+    if (versionDelegate is DynamicVersionDelegate &&
+        (oldVersion == null || oldVersion < currentVersion)) {
       // set version now, after migrations ran successfully
       await versionDelegate.setSchemaVersion(currentVersion);
     }
diff --git a/drift/test/engines/delegated_database_test.dart b/drift/test/engines/delegated_database_test.dart
index efd54a51..d0f6e5c8 100644
--- a/drift/test/engines/delegated_database_test.dart
+++ b/drift/test/engines/delegated_database_test.dart
@@ -109,14 +109,20 @@ void main() {
 
     test('when the database supports dynamic version', () async {
       final version = _MockDynamicVersionDelegate();
+      when(userDb.schemaVersion).thenReturn(3);
       when(version.schemaVersion).thenAnswer((_) => Future.value(3));
-
       when(delegate.versionDelegate).thenReturn(version);
       await db.ensureOpen(userDb);
 
       verify(delegate.open(userDb));
       verifyNever(delegate.runCustom(any, any));
       verify(version.schemaVersion);
+      // Running migrations from version 3 to 3
+      verifyNever(version.setSchemaVersion(3));
+
+      when(version.schemaVersion).thenAnswer((_) => Future.value(2));
+      await db.ensureOpen(userDb);
+      // Running migrations from version 2 to 3
       verify(version.setSchemaVersion(3));
     });