Magento 2.2.3 - ERROR 1062 (23000) at line 368677: Duplicate entry '0' for key 'PRIMARY'

Question

I used Magento Data Migration Tool to import my database test2_web2.sql from 1.9.2.2 to 2.2.3. Migration is successful with no issues.

If I export the database and then try to import it.

mysql -p -u test2_test test2_web2 < test2_web2.sql

The following error is displayed,

ERROR 1062 (23000) at line 368677: Duplicate entry '0' for key 'PRIMARY'

From my database Line 368677

ALTER TABLE cron_schedule

From within,

-- Indexes for table `cron_schedule`
--
**ALTER TABLE `cron_schedule`**
  ADD PRIMARY KEY (`schedule_id`),
  ADD KEY `CRON_SCHEDULE_JOB_CODE` (`job_code`),
  ADD KEY `CRON_SCHEDULE_SCHEDULED_AT_STATUS` (`scheduled_at`,`status`);

Does anyone know how I can resolve this?

Answer 1

This was resolved by manually deleting cron_schedule

Answer 2

In my case, the issue happens because the cron was running when importing.

The mysql dump I have is divided in 3 parts:

1. Table creation
2. Table key creation
3. Table increment setting

If the cron is run between steps 1 and 2, it will create some rows in the cron_schedule table with the schedule_id field = 0 as there's no increment set yet, so effectively when it reaches step 2 the key creation will fail as there is more than one row with schedule_id = 0 and schedule_id is part of the key.

Of course you can also create another structure in the backup to do the key creation right after table creation.