simultaneous read and writes to the RAMDirectory

[jian chen <ch...@gmail.com>]

Lucene gurus,

I have a question regarding RAMDirectory usage. Can the IndexWriter keep
adding documents to the index meanwhile the IndexReader is open on this
RAMDirectory and searches going on?

I know in a FSDirectory case, the IndexWriter can add documents to the index
meanwhile IndexReader reads from the index. This is because the IndexWriter
just writes new index files rather than modifying existing index files. The
only place (I remember) that the new and old indexes will conflict is the
segment file. Again, once the IndexWriter commits the change (by calling
close() method), the segment.new is renamed to segment atomically. Since the
old segment file is cached in memory by the IndexReader, so not a problem
for the IndexReader to serve search requests. The old segment file is cached
in memory, the other files pointed to by the old segment file are cached by
Linux anyway, or not removed by windows due to still being used.

Anyway, back to the RAMDirectory case. Having an IndexReader open while
IndexWriter adding documents to it, will that cause any issue?

Thanks,

Jian