OK, I decided to drop the index just to get things moving, and now I get a different error:

The database failed to upgrade. ERROR: The database configuration failed with the following message: The default schema does not exist. Please check log file for additional information (can be found in '/App_Data/Logs/UmbracoTraceLog.txt')

And in the logfile:

2017-08-09 12:36:47,820 [119] INFO Umbraco.Core.DatabaseContext - The database schema validation produced the following summary: The following tables were found in the database, but are not in the current schema: UFFieldConditions,UFFieldConditionRules,UFFieldSettings,UFFormStates,UFPrevalues,UFPrevalueSources,UFPrevalueSourceSettings,UFRecordFields,UFRecordDataBit,UFRecordDataDateTime,UFRecordDataInteger,UFRecordDataLongString,UFRecordDataString,UFRecords,MediaProtectIndex,UFSettings,MediaProtectAccess,UFUserFormSecurity,UFUserSecurity,UFWorkflowExecutionStates,UFWorkflows,UFWorkflowsToForms,umbracoDeployChecksum,umbracoDeployDependency,ConciergeLockUnLock,icUrlTracker,MediaProtectLog,UFForms,UFDataSources,UFDataSourceMappings,UFPages,UFFieldsets,UFFields,umbracoLock

The following columns were found in the database, but are not in the current schema: UFFieldConditions,Id,UFFieldConditions,Field,UFFieldConditions,Enabled,UFFieldConditions,ActionType,UFFieldConditions,LogicType,UFFieldConditionRules,Id,UFFieldConditionRules,FieldCondition,UFFieldConditionRules,Field,UFFieldConditionRules,Operator,UFFieldConditionRules,Value,UFFieldSettings,Field,UFFieldSettings,Key,UFFieldSettings,Value,UFFormStates,State,UFPrevalues,Id,UFPrevalues,Field,UFPrevalues,Value,UFPrevalues,SortOrder,UFPrevalueSources,Id,UFPrevalueSources,Name,UFPrevalueSources,Type,UFPrevalueSourceSettings,PrevalueProvider,UFPrevalueSourceSettings,Key,UFPrevalueSourceSettings,Value,UFRecordFields,Key,UFRecordFields,FieldId,UFRecordFields,Record,UFRecordFields,Alias,UFRecordFields,DataType,UFRecordDataBit,Id,UFRecordDataBit,Key,UFRecordDataBit,Value,UFRecordDataDateTime,Id,UFRecordDataDateTime,Key,UFRecordDataDateTime,Value,UFRecordDataInteger,Id,UFRecordDataInteger,Key,UFRecordDataInteger,Value,UFRecordDataLongString,Id,UFRecordDataLongString,Key,UFRecordDataLongString,Value,UFRecordDataString,Id,UFRecordDataString,Key,UFRecordDataString,Value,UFRecords,Id,UFRecords,Form,UFRecords,Created,UFRecords,Updated,UFRecords,CurrentPage,UFRecords,UmbracoPageId,UFRecords,IP,UFRecords,MemberKey,UFRecords,UniqueId,UFRecords,State,UFRecords,RecordData,MediaProtectIndex,IndexId,MediaProtectIndex,NodeId,MediaProtectIndex,UmbracoFolder,MediaProtectIndex,IndexDateTime,UFSettings,Id,UFSettings,Key,UFSettings,Value,MediaProtectAccess,Id,MediaProtectAccess,NodeGuid,MediaProtectAccess,LoginNodeGuid,MediaProtectAccess,NoAccessNodeGuid,MediaProtectAccess,ProtectionType,MediaProtectAccess,UserName,MediaProtectAccess,Roles,MediaProtectAccess,LastUpdateDate,UFUserFormSecurity,User,UFUserFormSecurity,Form,UFUserFormSecurity,HasAccess,UFUserFormSecurity,SecurityType,UFUserFormSecurity,AllowInEditor,UFUserFormSecurity,Id,UFUserSecurity,User,UFUserSecurity,ManageDataSources,UFUserSecurity,ManagePreValueSources,UFUserSecurity,ManageWorkflows,UFUserSecurity,ManageForms,UFUserSecurity,Id,UFWorkflowExecutionStates,Workflow,UFWorkflowExecutionStates,State,UFWorkflowExecutionStates,Form,UFWorkflows,Id,UFWorkflows,Name,UFWorkflows,Type,UFWorkflows,SortOrder,UFWorkflows,Active,UFWorkflows,Form,UFWorkflows,ExecutesOn,UFWorkflowsToForms,Workflow,UFWorkflowsToForms,Form,umbracoDeployChecksum,id,umbracoDeployChecksum,entityType,umbracoDeployChecksum,entityGuid,umbracoDeployChecksum,entityPath,umbracoDeployChecksum,localChecksum,umbracoDeployChecksum,compositeChecksum,umbracoDeployDependency,sourceId,umbracoDeployDependency,targetId,umbracoDeployDependency,mode,ConciergeLockUnLock,ticketId,ConciergeLockUnLock,nodeId,ConciergeLockUnLock,userId,ConciergeLockUnLock,Datestamp,ConciergeLockUnLock,Status,ConciergeLockUnLock,Comment,icUrlTracker,Id,icUrlTracker,OldUrl,icUrlTracker,OldUrlQueryString,icUrlTracker,OldRegex,icUrlTracker,RedirectRootNodeId,icUrlTracker,RedirectNodeId,icUrlTracker,RedirectUrl,icUrlTracker,RedirectHttpCode,icUrlTracker,RedirectPassThroughQueryString,icUrlTracker,ForceRedirect,icUrlTracker,Notes,icUrlTracker,Is404,icUrlTracker,Referrer,icUrlTracker,Inserted,MediaProtectLog,LogId,MediaProtectLog,MediaId,MediaProtectLog,Path,MediaProtectLog,Protected,MediaProtectLog,UserName,MediaProtectLog,UserIP,MediaProtectLog,LogDateTime,UFForms,Id,UFForms,Name,UFForms,Created,UFForms,ManualApproval,UFForms,GotoPageOnSubmit,UFForms,MessageOnSubmit,UFForms,DataSource,UFForms,ShowValidationSummary,UFForms,HideFieldValidation,UFForms,RequiredErrorMessage,UFForms,InvalidErrorMessage,UFForms,FieldIndicationType,UFForms,Indicator,UFForms,Archived,UFForms,StoreRecordsLocally,UFForms,DisableDefaultStylesheet,UFForms,Entries,UFForms,Views,UFDataSources,Id,UFDataSources,Type,UFDataSources,Name,UFDataSourceMappings,DataSource,UFDataSourceMappings,DataSourceField,UFDataSourceMappings,Form,UFDataSourceMappings,PrevalueTable,UFDataSourceMappings,PrevalueKeyField,UFDataSourceMappings,PrevalueValueField,UFDataSourceMappings,DataType,UFDataSourceMappings,DefaultValue,UFPages,Id,UFPages,Form,UFPages,SortOrder,UFPages,Caption,UFFieldsets,Id,UFFieldsets,Page,UFFieldsets,SortOrder,UFFieldsets,Caption,UFFields,Id,UFFields,Fieldset,UFFields,Fieldtype,UFFields,PreValueProvider,UFFields,RegEx,UFFields,Mandatory,UFFields,SortOrder,UFFields,Caption,UFFields,DataSourceField,UFFields,ToolTip,UFFields,DefaultValue,UFFields,RequiredErrorMessage,UFFields,InvalidErrorMessage,cmsMacro,uniqueId,cmsMacroProperty,uniquePropertyId,umbracoRelationType,typeUniqueId,umbracoLock,id,umbracoLock,value,umbracoLock,name

The following constraints (Primary Keys, Foreign Keys and Indexes) were found in the database, but are not in the current schema: FKcmsContentumbracoNode,FKcmsContentTypeumbracoNode,FKcmsContentVersioncmsContent,FKcmsContentXmlcmsContent,FKcmsDataTypeumbracoNode,FKcmsDataTypePreValuescmsDataType,FKcmsDocumentcmsContent,FKcmsDocumentcmsTemplate,FKcmsDocumentumbracoNode,FKcmsDocumentTypecmsContentType,FKcmsDocumentTypecmsTemplate,FKcmsDocumentTypeumbracoNode,FKcmsLanguageTextcmsDictionary,FKcmsMacroPropertycmsMacro,FKcmsMembercmsContent,FKcmsMemberumbracoNode,FKcmsMember2MemberGroupcmsMember,FKcmsMember2MemberGroupumbracoNode,FKcmsMemberTypecmsContentType,FKcmsMemberTypeumbracoNode,FKcmsPreviewXmlcmsContent,FKcmsPreviewXmlcmsContentVersion,FKcmsPropertyDatacmsPropertyType,FKcmsPropertyDataumbracoNode,FKcmsPropertyTypecmsContentType,FKcmsPropertyTypecmsDataType,FKcmsPropertyTypecmsTab,FKcmsTabcmsContentType,FKcmsTagRelationshipumbracoNodeid,FKcmsTaskcmsTaskType,FKcmsTaskumbracoNode,FKUFDataSourceMappingsUFDataSources,FKUFDataSourceMappingsUFForms,FKUFFieldUFFieldsets,FKUFFieldConditionRulesUFFieldConditions,FKUFFieldConditionRulesUFFields,FKUFFieldConditionsUFFields,FKUFFieldsetsUFPages,FKUFFieldSettingsUFFields,FKUFPagesUFForms,FKUFPrevaluesUFFields,FKUFPrevalueSettingsUFPrevalueProviders,FKUFRecordDataBitUFRecordFieldsKey,FKUFRecordDataDateTimeUFRecordFieldsKey,FKUFRecordDataIntegerUFRecordFieldsKey,FKUFRecordDataLongStringUFRecordFieldsKey,FKUFRecordDataStringUFRecordFieldsKey,FKUFWorkflowExecutionStatesUFFormStates,FKUFWorkflowsUFForms,FKumbracoDeployDependencyumbracoDeployChecksumid1,FKumbracoDeployDependencyumbracoDeployChecksumid2,FKumbracoDomainsumbracoNode,FKumbracoExternalLoginumbracoUserid,FKumbracoNodeumbracoNode,FKumbracoRelationumbracoRelationType,FKumbracoUser2NodeNotifyumbracoNode,FKumbracoUser2NodeNotifyumbracoUser,FKumbracoUser2NodePermissionumbracoNode,FKumbracoUser2NodePermissionumbracoUser,FKuseruserType,FKumbracoNodeumbracoNodeid,FKcmsContentTypeumbracoNodeid,FKcmsContentumbracoNodeid,FKcmsContentVersioncmsContentnodeId,FKcmsDocumentumbracoNodeid,FKcmsDocumentcmsContentnodeId,FKcmsDocumentcmsTemplatenodeId,FKcmsDocumentTypeumbracoNodeid,FKcmsDocumentTypecmsContentTypenodeId,FKcmsDocumentTypecmsTemplatenodeId,FKcmsDataTypeumbracoNodeid,FKcmsDataTypePreValuescmsDataTypenodeId,FKcmsLanguageTextcmsDictionaryid,FKumbracoDomainsumbracoNodeid,FKcmsMacroPropertycmsMacroid,FKcmsMemberTypecmsContentTypenodeId,FKcmsMemberTypeumbracoNodeid,FKcmsMembercmsContentnodeId,FKcmsMemberumbracoNodeid,FKcmsMember2MemberGroupcmsMembernodeId,FKcmsMember2MemberGroupumbracoNodeid,FKcmsContentXmlcmsContentnodeId,FKcmsPreviewXmlcmsContentnodeId,FKcmsPreviewXmlcmsContentVersionVersionId,FKcmsPropertyTypeGroupcmsContentTypenodeId,FKcmsPropertyTypecmsDataTypenodeId,FKcmsPropertyTypecmsContentTypenodeId,FKcmsPropertyTypecmsPropertyTypeGroupid,FKcmsPropertyDataumbracoNodeid,FKcmsPropertyDatacmsPropertyTypeid,FKumbracoRelationumbracoRelationTypeid,FKcmsTagRelationshipcmsTagsid,FKumbracoUserumbracoUserTypeid,FKcmsTaskcmsTaskTypeid,FKcmsTaskumbracoNodeid,FKcmsContentType2ContentTypeumbracoNodeparent,FKcmsContentType2ContentTypeumbracoNodechild,FKumbracoUser2appumbracoUserid,FKumbracoUser2NodeNotifyumbracoUserid,FKumbracoUser2NodeNotifyumbracoNodeid,FKumbracoUser2NodePermissionumbracoUserid,FKumbracoUser2NodePermissionumbracoNodeid,FKumbracoRedirectUrlumbracoNodeuniqueID,PKcmsConte3213E83F434ECFAF,PKMediaPro5E54864868487DD7,PKcmsTab,PKConciergeLockUnLock,PKdomains,PKicUrlTracker,PKlanguage,PKmacro,PKmacroProperty,PKMediaProtectAccess,PKMediaProtectIndex,PKtemplates,PKUFDataSourceMappings,PKUFDataSources,PKUFField,PKUFFieldConditionRules,PKUFFieldConditions,PKUFFieldsets,PKUFForms,PKUFFormStates,PKUFPages,PKUFPrevalueProviders,PKUFPrevalues,PKUFPrevalueSettings,PKUFRecordDataBit,PKUFRecordDataDateTime,PKUFRecordDataInteger,PKUFRecordDataLongString,PKUFRecordDataString,PKUFRecordFields,PKUFRecords,PKUFUserFormSecurity,PKUFUserSecurity,PKUFWorkflowExecutionStates,PKUFWorkflows,PKUFWorkflowsToForms,PKumbracoDeployChecksum,PKumbracoDeployDependency,PKumbracoMigrations,PKuserType,PKcmsTemplate,PKcmsContentVersion,PKumbracoLanguage,PKumbracoDomains,PKcmsMacro,PKcmsMacroProperty,PKcmsPropertyTypeGroup,PKumbracoUserType,PKumbracoMigration,PKumbracoLock,IXcmsContentVersion,IXcmsDataType,IXcmsDictionary,IXcmsTaskType,IXcmsTemplate,IXumbracoUser,IXumbracoNodeTrashed,IXumbracoNodeParentId,IXumbracoNodePath,IXumbracoNodeUniqueID,IXumbracoNodeObjectType,IXcmsContentTypeicon,IXcmsTemplatenodeId,IXcmsContentVersionContentId,IXcmsContentVersionVersionId,IXcmsDocumentpublished,IXcmsDocumentnewest,IXcmsDataTypenodeId,IXcmsDictionaryid,IXumbracoLanguagelanguageISOCode,IXumbracoLog,IXcmsMacroUniqueId,IXcmsMacroPropertyAlias,IXcmsMacroPropertyUniquePropertyId,IXcmsMacroPropertyAlias,IXcmsMemberLoginName,IXcmsPropertyTypeGroupUniqueID,IXcmsPropertyTypeUniqueID,IXcmsPropertyData1,IXcmsPropertyData2,IXcmsPropertyData3,IXumbracoRelationTypeUniqueId,IXumbracoRelationTypename,IXumbracoRelationTypealias,IXumbracoRelationparentChildType,IXcmsTags,IXumbracoUseruserLogin,IXcmsTaskTypealias,IXumbracoUser2NodePermissionnodeId,IXcomputerName,IXumbracoServerisActive,IXumbracoAccessnodeId,IXumbracoAccessRule,IXumbracoMigration,IXumbracoRedirectUrl

The following indexes were found in the database, but are not in the current schema: IXIcon,IXcmsContentVersion,IXcmsDataType,IXcmsDictionary,IXcmsMacroAlias,IXcmsPropertyData,IXcmsTaskType,IXcmsTemplate,IXicUrlTracker,IXIndexNodeId,IXIndexUmbracoFolder,IXumbracoDeployChecksum,IXumbracoUser,IXumbracoNodePath,IXumbracoNodeUniqueID,IXcmsContentTypeicon,IXcmsTemplatenodeId,IXcmsContentVersionVersionId,IXcmsDataTypenodeId,IXumbracoLanguagelanguageISOCode,IXcmsMacroUniqueId,IXcmsMacroPropertyAlias,IXcmsMacroPropertyUniquePropertyId,IXcmsMemberLoginName,IXumbracoRelationTypeUniqueId,IXumbracoRelationTypename,IXumbracoRelationTypealias,IXumbracoRelationparentChildType,IXumbracoUseruserLogin,IXcmsTaskTypealias,IXumbracoUser2NodePermissionnodeId,IXumbracoMigration

The following unknown constraints (Primary Keys, Foreign Keys and Indexes) were found in the database, but are not in the current schema: cmsTags_cmsTagRelationship

2017-08-09 12:36:47,820 [119] ERROR Umbraco.Web.Install.Controllers.InstallApiController - Installation step DatabaseUpgrade failed. System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> Umbraco.Web.Install.InstallException: The database failed to upgrade. ERROR: The database configuration failed with the following message: The default schema does not exist. Please check log file for additional information (can be found in '/AppData/Logs/UmbracoTraceLog.txt') at Umbraco.Web.Install.InstallSteps.DatabaseUpgradeStep.Execute(Object model) --- End of inner exception stack trace --- at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at Umbraco.Web.Install.Controllers.InstallApiController.ExecuteStep(InstallSetupStep step, JToken instruction) at Umbraco.Web.Install.Controllers.InstallApiController.PostPerformInstall(InstallInstructions installModel) 2017-08-09 12:36:47,821 [119] INFO Umbraco.Web.Install.Controllers.InstallApiController - Step completed (took 18665ms) 2017-08-09 12:36:47,821 [119] ERROR Umbraco.Web.Install.Controllers.InstallApiController - An error occurred during installation step DatabaseUpgrade System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> Umbraco.Web.Install.InstallException: The database failed to upgrade. ERROR: The database configuration failed with the following message: The default schema does not exist. Please check log file for additional information (can be found in '/AppData/Logs/UmbracoTraceLog.txt') at Umbraco.Web.Install.InstallSteps.DatabaseUpgradeStep.Execute(Object model) --- End of inner exception stack trace --- at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at Umbraco.Web.Install.Controllers.InstallApiController.ExecuteStep(InstallSetupStep step, JToken instruction) at Umbraco.Web.Install.Controllers.InstallApiController.PostPerformInstall(InstallInstructions installModel)

Progress. I think.

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