Document work around when upgrading to 9.3/9.4 for MySql instances.

doc/update/9.2-to-9.3.md

@@ -294,6 +294,31 @@ sudo -u git -H bundle exec rake yarn:install gitlab:assets:clean gitlab:assets:c
 sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
 ```
 
+**Error in migrations for MySQL installations**:
+
+When running migrations it's very likely you found the following error:
+
+```
+undefined method `plan' for #<Group:0x007f52ebe98c80>...
+```
+
+Please use this work around for source installations:
+
+```
+sudo -u git -H bundle exec rake db:migrate:up VERSION=20170512131952 RAILS_ENV=production
+sudo -u git -H bundle exec rake db:migrate
+
+# Now continue from the "Compile GetText PO files" step.
+```
+
+Please use this work around for Omnibus installations:
+
+```
+sudo gitlab-rake db:migrate:up VERSION=20170512131952
+sudo gitlab-rake db:migrate
+sudo gitlab-ctl reconfigure
+```
+
 **MySQL installations**: Run through the `MySQL strings limits` and `Tables and data conversion to utf8mb4` [tasks](../install/database_mysql.md).
 
 ### 13. Start application

doc/update/9.3-to-9.4.md

@@ -307,6 +307,31 @@ sudo -u git -H bundle exec rake yarn:install gitlab:assets:clean gitlab:assets:c
 sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
 ```
 
+**Error in migrations for MySQL installations**:
+
+When running migrations it's very likely you found the following error:
+
+```
+undefined method `plan' for #<Group:0x007f52ebe98c80>...
+```
+
+Please use this work around for source installations:
+
+```
+sudo -u git -H bundle exec rake db:migrate:up VERSION=20170512131952 RAILS_ENV=production
+sudo -u git -H bundle exec rake db:migrate
+
+# Now continue from the "Compile GetText PO files" step.
+```
+
+Please use this work around for Omnibus installations:
+
+```
+sudo gitlab-rake db:migrate:up VERSION=20170512131952
+sudo gitlab-rake db:migrate
+sudo gitlab-ctl reconfigure
+```
+
 **MySQL installations**: Run through the `MySQL strings limits` and `Tables and data conversion to utf8mb4` [tasks](../install/database_mysql.md).
 
 ### 13. Start application