Fix workaround foreign key checks

app.js

@@ -75,11 +75,15 @@ global.syzoj = {
     global.Promise = Sequelize.Promise;
     this.db.countQuery = async (sql, options) => (await this.db.query(`SELECT COUNT(*) FROM (${sql}) AS \`__tmp_table\``, options))[0][0]['COUNT(*)'];
 
-    if (this.config.db.dialect.toLowerCase() === 'mysql') {
-      await this.db.query('SET foreign_key_checks = 0;');
-    } else if (this.config.db.dialect.toLowerCase() === 'sqlite') {
-      await this.db.query('PRAGMA foreign_keys = OFF;');
-    } else {
+    this.db.workAroundForeignKeyChecks = async () => {
+      if (this.config.db.dialect.toLowerCase() === 'mysql') {
+        await this.db.query('SET foreign_key_checks = 0;');
+      } else if (this.config.db.dialect.toLowerCase() === 'sqlite') {
+        await this.db.query('PRAGMA foreign_keys = OFF;');
+      }
+    }
+
+    if (!['mysql', 'sqlite'].includes(this.config.db.dialect.toLowerCase())) {
       this.log('Unsupported database: ' + this.config.db.dialect);
       process.exit();
     }

models/problem.js

@@ -428,6 +428,7 @@ class Problem extends Model {
 
   async changeID(id) {
     id = parseInt(id);
+    await db.workAroundForeignKeyChecks();
     await db.query('UPDATE `problem`         SET `id`         = ' + id                      + ' WHERE `id`         = ' + this.id);
     await db.query('UPDATE `judge_state`     SET `problem_id` = ' + id                      + ' WHERE `problem_id` = ' + this.id);
     await db.query('UPDATE `problem_tag_map` SET `problem_id` = ' + id                      + ' WHERE `problem_id` = ' + this.id);