I have read a lot about IndexWriter and multi-threading over the Internet. It seems to me that the normal practice is:
1) use a same indexwriter instance for multiple threads; 2) create an individual RAMDirectory per threads; 3) use addIndexes(Directory[]) methods to add to a local drive folder all the indexes stored in the ram directories of the threads. My question are: a) For 1), the IndexWriter instance must be associated with a lucene Directory, right? Let us assume it is built on a FSDirectory, then what is the purpose to use this FSDirectory-built indexwriter in 2), where the documents are added into a RAMDirectory? That being said, there must be a new index writer created upon a RAMDirectory in each thread. If it is the case, we should create a RAMDirectory-built writer in each thread, rather than use a FSDirectory-built writer cross multiple threads. b) For 3), the writer presumed to perform the addIndexes(Directory[]) function seems to be the same one created in 1). Within each thread, the index writer needs to close to make new documents visible to the searcher of that thread. So, since the writer has been closed in each or more of the threads, how can this writer be used outside the thread run functions to add all the RAMDirectories? Am I missing something? Thanks
