: Closing an IndexReader only flushes the list of deleted docids to the : index... it doesn't actually delete them. Deletions only happen when : the deleted docs segment is involved in a merge, or when an optimize : is done (which is a merge of all segments).
just to clarify slightly because "deleted" can be differnet things to differnet people... think of executing a delete command as "logically" deleting them, by adding them to a list of documents to be ignored by IndexSearchers. a commit will ensure that deleted docs list is written to disk, and reopen the IndexSearcher which will treat any documents in that list as if they didn't exit. When segment merges happens sometime in the future document information is "physically" deleted in the sense that the data associated with docs i nthe deleted list is actually removed from the index files, and disk/ram space is freed up. -Hoss
