In order to offer user's near realtime search, without incurring
an indexing performance penalty, we can implement search on
IndexWriter's RAM buffer. This is the buffer that is filled in
RAM as documents are indexed. Currently the RAM buffer is
flushed to the underlying directory (usually disk) before being
Todays Lucene based NRT systems must incur the cost of merging
segments, which can slow indexing.
Michael Busch has good suggestions regarding how to handle deletes using max doc ids.
The area that isn't fully fleshed out is the terms dictionary,
which needs to be sorted prior to queries executing. Currently
IW implements a specialized hash table. Michael B has a