title: Select items in TypeORM migration
body: <p>I'm trying to add one more column to a table. Additionally, I have to insert an object in created column based on existing data. The problem is when I'm modifying the table, I'm trying to select all items from the table but the query is stuck (see &quot;Get events&quot; in log).</p>
  <p>Here is my code:</p>
  <pre><code>    async up(queryRunner: QueryRunner): Promise&lt;any&gt; {
          Logger.debug('Start migration');
          Logger.debug('Table modification');
          await queryRunner.addColumn(
              'sport_events',
              new TableColumn({
                  name: 'url_keys',
                  type: 'hstore',
                  isNullable: true,
              }),
          );
  
          Logger.debug('Create repo');
          const repo = queryRunner.connection.getRepository(SportEvent);
  
          Logger.debug('Get events');
          let events = await repo.createQueryBuilder().getMany();
  
          Logger.debug('Modify events');
          events = events.map((event) =&gt; {
              const keys = {};
  
              for (const [key, val] of Object.entries(event.name)) {
                  keys[key] = generateURLId(val as string, key);
              }
  
              event.URLKeys = keys;
              return event;
          });
  
          Logger.debug('Save modified events');
          await repo.save(events);
  
          Logger.debug('Done');
      }
  </code></pre>
  <p>Log:</p>
  <pre><code>[Nest] 25628   - 07/17/2020, 12:00:28 PM   Start migration +504ms
  [Nest] 25628   - 07/17/2020, 12:00:28 PM   Table modification +0ms
  [Nest] 25628   - 07/17/2020, 12:00:28 PM   Create repo +454ms
  [Nest] 25628   - 07/17/2020, 12:00:28 PM   Get events +0ms
  </code></pre>