Selectively configure flushing in initial sync.

packages/powersync/lib/src/bucket_storage.dart

@@ -45,14 +45,6 @@ class BucketStorage {
     return rows.first['client_id'] as String;
   }
 
-  Future<void> streamOp(String op) async {
-    await writeTransaction((tx) async {
-      await tx.execute(
-          'INSERT INTO powersync_operations(op, data) VALUES(?, ?)',
-          ['stream', op]);
-    });
-  }
-
   Future<void> saveSyncData(SyncDataBatch batch) async {
     var count = 0;
 
@@ -65,7 +57,10 @@ class BucketStorage {
               'buckets': [b]
             }));
       }
-    });
+      // No need to flush - the data is not directly visible to the user either way.
+      // We get major initial sync performance improvements with IndexedDB by
+      // not flushing here.
+    }, flush: false);
     _compactCounter += count;
   }
 
@@ -85,7 +80,8 @@ class BucketStorage {
       await tx.execute(
           'INSERT INTO powersync_operations(op, data) VALUES(?, ?)',
           ['delete_bucket', bucket]);
-    });
+      // No need to flush - not directly visible to the user
+    }, flush: false);
 
     _pendingBucketDeletes = true;
   }
@@ -125,7 +121,8 @@ class BucketStorage {
             "UPDATE ps_buckets SET last_op = ? WHERE name = '\$local'",
             [checkpoint.writeCheckpoint]);
       }
-    });
+      // Not flushing here - the flush will happen in the next step
+    }, flush: false);
 
     final valid = await updateObjectsFromBuckets(checkpoint);
     if (!valid) {
@@ -150,7 +147,10 @@ class BucketStorage {
         // can_update_local(db) == false
         return false;
       }
-    });
+      // Important to flush here.
+      // After this step, the synced data will be visible to the user,
+      // and we don't want that to be reverted.
+    }, flush: true);
   }
 
   Future<SyncLocalDatabaseResult> validateChecksums(
@@ -176,39 +176,25 @@ class BucketStorage {
   }
 
   Future<void> autoCompact() async {
+    // This is a no-op since powersync-sqlite-core v0.3.0
+
     // 1. Delete buckets
     await _deletePendingBuckets();
 
     // 2. Clear REMOVE operations, only keeping PUT ones
     await _clearRemoveOps();
-
-    // await _compactWal();
-  }
-
-  // ignore: unused_element
-  Future<void> _compactWal() async {
-    try {
-      await writeTransaction((tx) async {
-        await tx.execute('PRAGMA wal_checkpoint(TRUNCATE)');
-      });
-    } on SqliteException catch (e) {
-      // Ignore SQLITE_BUSY
-      if (e.resultCode == 5) {
-        // Ignore
-      } else if (e.resultCode == 6) {
-        // Ignore
-      }
-    }
   }
 
   Future<void> _deletePendingBuckets() async {
+    // This is a no-op since powersync-sqlite-core v0.3.0
     if (_pendingBucketDeletes) {
       // Executed once after start-up, and again when there are pending deletes.
       await writeTransaction((tx) async {
         await tx.execute(
             'INSERT INTO powersync_operations(op, data) VALUES (?, ?)',
             ['delete_pending_buckets', '']);
-      });
+        // No need to flush - not directly visible to the user
+      }, flush: false);
       _pendingBucketDeletes = false;
     }
   }
@@ -218,11 +204,13 @@ class BucketStorage {
       return;
     }
 
+    // This is a no-op since powersync-sqlite-core v0.3.0
     await writeTransaction((tx) async {
       await tx.execute(
           'INSERT INTO powersync_operations(op, data) VALUES (?, ?)',
           ['clear_remove_ops', '']);
-    });
+      // No need to flush - not directly visible to the user
+    }, flush: false);
     _compactCounter = 0;
   }
 
@@ -267,7 +255,8 @@ class BucketStorage {
           [opId]);
 
       return true;
-    });
+      // Flush here - don't want to lose the write checkpoint updates.
+    }, flush: true);
   }
 
   Future<CrudEntry?> nextCrudItem() async {
@@ -313,7 +302,8 @@ class BucketStorage {
               await tx.execute(
                   'UPDATE ps_buckets SET target_op = $maxOpId WHERE name=\'\$local\'');
             }
-          });
+            // Flush here - don't want to lose the write checkpoint updates.
+          }, flush: true);
         });
   }
 
@@ -323,7 +313,8 @@ class BucketStorage {
   /// concurrently.
   Future<T> writeTransaction<T>(
       Future<T> Function(SqliteWriteContext tx) callback,
-      {Duration? lockTimeout}) async {
+      {Duration? lockTimeout,
+      required bool flush}) async {
     return _internalDb.writeTransaction(callback, lockTimeout: lockTimeout);
   }
 }

packages/powersync/lib/src/web/sync_worker.dart

@@ -16,8 +16,8 @@ import 'package:powersync/src/streaming_sync.dart';
 import 'package:sqlite_async/web.dart';
 import 'package:web/web.dart' hide RequestMode;
 
-import '../bucket_storage.dart';
 import 'sync_worker_protocol.dart';
+import 'web_bucket_storage.dart';
 
 final _logger = autoLogger;
 
@@ -258,7 +258,7 @@ class _SyncRunner {
         : jsonDecode(syncParamsEncoded!) as Map<String, dynamic>;
 
     sync = StreamingSyncImplementation(
-        adapter: BucketStorage(database),
+        adapter: WebBucketStorage(database),
         credentialsCallback: client.channel.credentialsCallback,
         invalidCredentialsCallback: client.channel.invalidCredentialsCallback,
         uploadCrud: client.channel.uploadCrud,

packages/powersync/lib/src/web/web_bucket_storage.dart

@@ -0,0 +1,20 @@
+import 'package:powersync/sqlite_async.dart';
+import 'package:powersync/src/bucket_storage.dart';
+import 'package:sqlite_async/web.dart';
+
+class WebBucketStorage extends BucketStorage {
+  final WebSqliteConnection _webDb;
+
+  WebBucketStorage(this._webDb) : super(_webDb);
+
+  @override
+
+  /// Override to implement the flush parameter for web.
+  Future<T> writeTransaction<T>(
+      Future<T> Function(SqliteWriteContext tx) callback,
+      {Duration? lockTimeout,
+      required bool flush}) async {
+    return _webDb.writeTransaction(callback,
+        lockTimeout: lockTimeout, flush: flush);
+  }
+}