If there is huge number of groups and users, the upgrade process in so-hook could take hours to complete
Quote from email:
"In the SO upgrade: com.liferay.so.hook.upgrade.v3_0_0.UpgradeGroup, we iterate thru every single Group in the system and check to see if it’s an SO Group. The check is a check of an expand value. This is ridiculously bad since there are thousands of groups"