question: provides a function to modify index meta data when an index is introduced into the cluster state for the first time . plugins should return the input index metadata via unaryoperator #identity if no upgrade is required . the order of the index upgrader calls for the same index is undefined and can change between runs so , it is expected that plugins will modify only indices owned by them to avoid conflicts . concode_field_sep PlaceHolder placeHolder concode_field_sep List<ExecutorBuilder<?>> getExecutorBuilders concode_elem_sep List<BootstrapCheck> getBootstrapChecks concode_elem_sep List<Setting<?>> getSettings concode_elem_sep void onIndexModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep void onModule concode_elem_sep List<NamedXContentRegistry.Entry> getNamedXContent concode_elem_sep UnaryOperator<Map<String,MetaData.Custom>> getCustomMetaDataUpgrader concode_elem_sep Collection<Class<? extends LifecycleComponent>> getGuiceServiceClasses concode_elem_sep Collection<Module> createGuiceModules concode_elem_sep Collection<Object> createComponents concode_elem_sep List<String> getSettingsFilter concode_elem_sep Settings additionalSettings concode_elem_sep List<NamedWriteableRegistry.Entry> getNamedWriteables concode_elem_sep UnaryOperator<Map<String,IndexTemplateMetaData>> getIndexTemplateMetaDataUpgrader concode_elem_sep void close
target: UnaryOperator < IndexMetaData > function ( ) { return UnaryOperator . identity ( ) ; }