Unable to upgrade Plesk: Duplicate entry for key 'guid'

Symptoms

Unable to upgrade Plesk with the following error message: 

CONFIG_TEXT: Migration failed: 18.0.31/2020-09-28-06-53-58_add_unique_guid_to_domains.php
Query failed: ALTER TABLE `domains` ADD UNIQUE KEY `guid` (`guid` ASC)
Duplicate entry '3ebe939b-c58c-4a56-a3e4-98750d90b157' for key 'guid' 

Cause

Database inconsistency, two different domains have the same GUID. 

Resolution 

1. Log into the server via SSH.

2. Create a backup for psa database:
   

   # plesk db dump psa > /root/psa.sql

3. Execute the command below to find ID of the domains that have the same GUID:
   

   # plesk db "select id from domains where guid='3ebe939b-c58c-4a56-a3e4-98750d90b157'\G;"
   *************************** 1. row ***************************
   id: 137
   
   *************************** 2. row ***************************
   id: 338

4. Manually generate a new GUID by changing several symbols of the GUID from the error, for example from:
   

   CONFIG_TEXT: 3ebe939b-c58c-4a56-a3e4-98750d90b157
   

   To

   CONFIG_TEXT: 3ebe939b-c58c-4a56-a3e4-98750d90b378

5. Using the command below, verify that the newly generated GUID is not assigned to any domain:

   # plesk db "select guid,id from domains where guid='3ebe939b-c58c-4a56-a3e4-98750d90b378'\G;"
   #

6. Run the command below to set newly generated GUID to one of the domains ID from step №3:
   

   # plesk db "update domains set guid='3ebe939b-c58c-4a56-a3e4-98750d90b378' where id=137;"

7. Re-run the Plesk upgrade.