I like my Magento database as clean as possible so whenever I uninstall an extension I also remove all data that was stored by this particular module from the database.
Now I noticed that there is some data stored in the extra column of the Admin_User Table too. It lists many old modules that I have removed in the past.
What is the purpose of this column and is it safe to remove the data that is related to exensions that are no longer installed?
In theory you can set a lot of things in the extra column in a serialized format.
But the core uses this to remember the expanded/collapsed fieldsets in the system->configuration sections.
So each time you expand/collapse a config fieldset a request is made to admin/system_config/state/?container={fieldset_id}&value={1-expanded|0-collapsed}.
the container name and value are saved in the extra column (see method Mage_Adminhtml_System_ConfigController::stateAction) and is later retrieved in the method Mage_Adminhtml_Block_System_Config_Form_Fieldset::_getCollapseState so you will see the fieldset just like you left it (expanded|collapsed).
I strongly advice on keeping the column.
You can remove the data from it, but this means that the next time you visit a system->cofiguration section all fieldsets will be collapsed.
extra column in the Admin_User Table (just the value, not the column itself). This doesn't seem to cause any issues at all. After saving the config again a new value is stored into the extra column. All references to the old uninstalled extension are gone now.
Commented
Jan 27, 2015 at 10:28