TYPO3 Core

During the upgrade to version 12 with a lot of entries in sys_log , SysLogSerializationUpdate takes quite a lot of time because it processes each row individually. This however is only necessary for rows where log_data is not a:0:{}. I suggest adding a fast update command on all rows that have that value stored and afterwards process all other rows:

update sys_log set log_data = '[]' where log_data = 'a:0:{}';