Unfortunately my update/upgrade has failed.
I've done my best to follow the instructions on this page: https://docs.civicrm.org/sysadmin/en/latest/upgrade/wordpress/
Made it as far as the "Upgrade the database" instruction, by pointing my browser to the indicated url: http://example.org/wp-admin/admin.php?page=CiviCRM&q=civicrm/upgrade&reset=1
I gave it permission to proceed, and the progress bar began showing progress. Unfortunately when it hit 5.20 it stalled and sat there for a very long time.
It finally exited, incomplete. What was left on the system was not functional.
I've managed to back out and have reverted to the former system by re-naming my CiviCRM directory. I never deleted the original, as suggested in the instruction page. Rather, I renamed it civicrm.bak, in case something bad happened (and it did).
Where from here? My CiviCRM system status now indicates: Database Partially Upgraded Database check failed - the database looks to have been partially upgraded. You must reload the database with the backup and try the upgrade process again.
Were I to go through the same steps again, should I expect anything different? Or, will it merely repeat the problem?
Should I have tried to do this in a greater number of smaller increments?
Thank you.
Here is the most recent entry in the ConfigAndLog file. I've replaced our actual login id with "loginID":
Dec 28 12:45:02 [debug] $backTrace = #0 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/Error.php(915): CRM_Core_Error::backtrace("backTrace", TRUE)
#1 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/vendor/pear/pear-core-minimal/src/PEAR.php(922): CRM_Core_Error::exceptionHandler(Object(DB_Error))
#2 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB.php(997): PEAR_Error->__construct("DB Error: no such field", -19, 16, (Array:2), "SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#3 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/vendor/pear/pear-core-minimal/src/PEAR.php(575): DB_Error->__construct(-19, 16, (Array:2), "SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#4 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/vendor/pear/pear-core-minimal/src/PEAR.php(223): PEAR->_raiseError(Object(DB_mysqli), NULL, -19, 16, (Array:2), "SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...", "DB_Error", TRUE)
#5 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/common.php(1925): PEAR->__call("raiseError", (Array:7))
#6 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/mysqli.php(935): DB_common->raiseError(-19, NULL, NULL, "SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...", "1054 ** Unknown column 'a.api_entity' in 'field list'")
#7 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/mysqli.php(405): DB_mysqli->mysqliRaiseError()
#8 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/common.php(1231): DB_mysqli->simpleQuery("SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#9 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/DataObject.php(2696): DB_common->query("SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#10 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/DataObject.php(1829): DB_DataObject->_query("SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#11 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/DAO.php(421): DB_DataObject->query("SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#12 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/DAO.php(1463): CRM_Core_DAO->query("SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...", TRUE)
#13 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/Api4/Query/Api4SelectQuery.php(117): CRM_Core_DAO::executeQuery("SELECT `a`.`id` AS `id`, `a`.`form_values` AS `form_values`, `a`.`mapping_id`...")
#14 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/Api4/Generic/DAOGetAction.php(59): Civi\Api4\Query\Api4SelectQuery->run()
#15 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/Api4/Generic/DAOGetAction.php(50): Civi\Api4\Generic\DAOGetAction->getObjects()
#16 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/Api4/Provider/ActionObjectProvider.php(68): Civi\Api4\Generic\DAOGetAction->_run(Object(Civi\Api4\Generic\Result))
#17 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Kernel.php(150): Civi\Api4\Provider\ActionObjectProvider->invoke(Object(Civi\Api4\Generic\DAOGetAction))
#18 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/Api4/Generic/AbstractAction.php(231): Civi\API\Kernel->runRequest(Object(Civi\Api4\Generic\DAOGetAction))
#19 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/SavedSearch.php(214): Civi\Api4\Generic\AbstractAction->execute()
#20 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/GroupContactCache.php(463): CRM_Contact_BAO_SavedSearch::getSearchParams("5")
#21 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(3192): CRM_Contact_BAO_GroupContactCache::load(Object(CRM_Core_DAO))
#22 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(3093): CRM_Contact_BAO_Query->addGroupContactCache((Array:1), "civicrm_group_contact_cache_5fea43ce068b3", "contact_a", "IN")
#23 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(1820): CRM_Contact_BAO_Query->group((Array:5))
#24 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(2058): CRM_Contact_BAO_Query->whereClauseSingle((Array:5), FALSE)
#25 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(582): CRM_Contact_BAO_Query->whereClause(FALSE)
#26 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(529): CRM_Contact_BAO_Query->initialize(NULL)
#27 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/Query.php(4610): CRM_Contact_BAO_Query->__construct((Array:1), (Array:1), (Array:131), TRUE, FALSE, 1, TRUE, TRUE, FALSE, NULL, "AND", NULL, 1)
#28 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/GroupContactCache.php(210): CRM_Contact_BAO_Query::apiQuery((Array:1), (Array:1), NULL, NULL, 0, 0, FALSE)
#29 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/BAO/GroupContactCache.php(192): CRM_Contact_BAO_GroupContactCache::add((Array:9))
#30 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/api/v3/Job.php(683): CRM_Contact_BAO_GroupContactCache::loadAll((Array:0), "Number optional-Limit the number of smart groups rebuild")
#31 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Provider/MagicFunctionProvider.php(89): civicrm_api3_job_group_rebuild((Array:2))
#32 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Kernel.php(150): Civi\API\Provider\MagicFunctionProvider->invoke((Array:8))
#33 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Kernel.php(81): Civi\API\Kernel->runRequest((Array:8))
#34 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/api/api.php(22): Civi\API\Kernel->runSafe("job", "group_rebuild", (Array:2))
#35 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/JobManager.php(133): civicrm_api("job", "group_rebuild", (Array:2))
#36 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/JobManager.php(66): CRM_Core_JobManager->executeJob(Object(CRM_Core_ScheduledJob))
#37 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/api/v3/Job.php(118): CRM_Core_JobManager->execute(FALSE)
#38 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Provider/MagicFunctionProvider.php(89): civicrm_api3_job_execute((Array:2))
#39 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Kernel.php(150): Civi\API\Provider\MagicFunctionProvider->invoke((Array:8))
#40 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/Civi/API/Kernel.php(81): Civi\API\Kernel->runRequest((Array:8))
#41 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/api/api.php(22): Civi\API\Kernel->runSafe("Job", "execute", (Array:2))
#42 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/bin/cli.class.php(122): civicrm_api("Job", "execute", (Array:2))
#43 /home/loginID/public_html/wp-content/plugins/civicrm/civicrm/bin/cli.php(32): civicrm_cli->callApi()
#44 {main}
UPDATE civicrm_domain SET version='5.16.2';
, or maybe 5.19.0 since you said it stopped around 5.20. For the log file, I'd search for the word "upgrade" - somewhere it should say something like "starting upgrade".