Add migration to fix the issue.

Author: rkistner

modules/module-postgres-storage/src/migrations/scripts/1746700486312-op-id-sequence.ts

@@ -0,0 +1,27 @@
+import { migrations } from '@powersync/service-core';
+
+import { openMigrationDB } from '../migration-utils.js';
+
+export const up: migrations.PowerSyncMigrationFunction = async (context) => {
+  const {
+    service_context: { configuration }
+  } = context;
+  await using client = openMigrationDB(configuration.storage);
+
+  await client.transaction(async (db) => {
+    // This ensures that op_id_sequence is initialized, so that
+    //   SELECT nextval('op_id_sequence')
+    // is always greater than
+    //   SELECT LAST_VALUE FROM op_id_sequence
+    // Without initializing, there is a case where last_value = 1, is_called = false, and the next call to nextval is also 1.
+    // This call is harmless if the sequence was already initialized - it would only increment the sequence by 1.
+    await db.sql`
+      SELECT
+        nextval('op_id_sequence');
+    `.execute();
+  });
+};
+
+export const down: migrations.PowerSyncMigrationFunction = async (context) => {
+  // No-op - no need to revert the initialization when migrating down.
+};