CRM-12928 Merge contacts fatal error: Unknown column 'source_contact_id' in 'where clause (related to activity restructure)

Merge contacts is broken. Clicking Merge Contacts action from Find Contacts throws this fatal error:
Unknown column 'source_contact_id' in 'where clause

------- complete backtrace -------------
#0 /Users/dgg/git/crm_v4.4/CRM/Core/Error.php(148): CRM_Core_Error::backtrace()
#1 [internal function](): CRM_Core_Error::handle(Object(DB_Error))
#2 /Users/dgg/git/crm_v4.4/packages/PEAR.php(931): call_user_func((Array:2), Object(DB_Error))
#3 /Users/dgg/git/crm_v4.4/packages/DB.php(969): PEAR_Error->PEAR_Error("DB Error: no such field", -19, 16, (Array:2), "SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204 ...")
#4 /Users/dgg/git/crm_v4.4/packages/PEAR.php(564): DB_Error->DB_Error(-19, 16, (Array:2), "SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204 ...")
#5 /Users/dgg/git/crm_v4.4/packages/DB/common.php(1905): PEAR->raiseError(NULL, -19, NULL, NULL, "SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204 ...", "DB_Error", TRUE)
#6 /Users/dgg/git/crm_v4.4/packages/DB/mysql.php(898): DB_common->raiseError(-19, NULL, NULL, NULL, "1054 ** Unknown column 'source_contact_id' in 'where clause'")
#7 /Users/dgg/git/crm_v4.4/packages/DB/mysql.php(327): DB_mysql->mysqlRaiseError()
#8 /Users/dgg/git/crm_v4.4/packages/DB/common.php(1216): DB_mysql->simpleQuery("SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204")
#9 /Users/dgg/git/crm_v4.4/packages/DB/DataObject.php(2421): DB_common->query("SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204")
#10 /Users/dgg/git/crm_v4.4/packages/DB/DataObject.php(1613): DB_DataObject->_query("SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204")
#11 /Users/dgg/git/crm_v4.4/CRM/Core/DAO.php(158): DB_DataObject->query("SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204")
#12 /Users/dgg/git/crm_v4.4/CRM/Core/DAO.php(947): CRM_Core_DAO->query("SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204", TRUE)
#13 /Users/dgg/git/crm_v4.4/CRM/Dedupe/Merger.php(177): CRM_Core_DAO::singleValueQuery("SELECT COUNT AS count FROM civicrm_activity WHERE source_contact_id = 204")
#14 /Users/dgg/git/crm_v4.4/CRM/Dedupe/Merger.php(1005): CRM_Dedupe_Merger::getActiveRelTables("204")
#15 /Users/dgg/git/crm_v4.4/CRM/Contact/Form/Merge.php(181): CRM_Dedupe_Merger::getRowsElementsAndInfo("50", "204")
#16 /Users/dgg/git/crm_v4.4/CRM/Core/Form.php(351): CRM_Contact_Form_Merge->preProcess()
#17 /Users/dgg/git/crm_v4.4/CRM/Core/QuickForm/Action/Display.php(93): CRM_Core_Form->buildForm()
#18 /Users/dgg/git/crm_v4.4/packages/HTML/QuickForm/Controller.php(203): CRM_Core_QuickForm_Action_Display->perform(Object(CRM_Contact_Form_Merge), "display")
#19 /Users/dgg/git/crm_v4.4/packages/HTML/QuickForm/Page.php(103): HTML_QuickForm_Controller->handle(Object(CRM_Contact_Form_Merge), "display")
#20 /Users/dgg/git/crm_v4.4/CRM/Core/Controller.php(315): HTML_QuickForm_Page->handle("display")
#21 /Users/dgg/git/crm_v4.4/CRM/Utils/Wrapper.php(117): CRM_Core_Controller->run()
#22 /Users/dgg/git/crm_v4.4/CRM/Core/Invoke.php(266): CRM_Utils_Wrapper->run("CRM_Contact_Form_Merge", "Merge Contact", NULL)
#23 /Users/dgg/git/crm_v4.4/CRM/Core/Invoke.php(70): CRM_Core_Invoke::runItem((Array:13))
#24 /Users/dgg/git/crm_v4.4/CRM/Core/Invoke.php(52): CRM_Core_Invoke::_invoke((Array:3))
#25 /Users/dgg/git/crm_v4.4/drupal/civicrm.module(436): CRM_Core_Invoke::invoke((Array:3))
#26 [internal function](): civicrm_invoke("contact", "merge")
#27 /Users/dgg/htdocs/drupal7/includes/menu.inc(517): call_user_func_array("civicrm_invoke", (Array:2))
#28 /Users/dgg/htdocs/drupal7/index.php(21): menu_execute_active_handler()
#29