The available search re-indexing operation always discards existing indexes and re-indexes all classes.
Search re-index takes an unnecessarily long time when only a single class needs to be re-indexed. Search operations are not able to use existing indexes until the re-index operation for the appropriate class is complete, so will not return good results.
Search re-index backing beans were updated to take a set of boolean options for each indexable class, which determine whether existing indexes for the class will be purged, whether re-index will be performed on entities of the class, and whether the index for the class will be optimized. These options are presented in a table on the "Manage Search" page under the Administration menu.
Classes can be re-indexed separately, allowing for shorter re-index time per operation. Existing indexes can be kept during re-indexing, so searches may be able to return good results during re-index.