The protocol runs over TCP/IP, or over other network protocols that provide ordered, lossless, bi-directional connections.
Deleting documents from a Lucene index is easy when you have a primary key field in your document (like in traditional SQL databases).
However, sometimes deleting a number of documents based on multiple fields in the document is what you need. The Lucene API allows you to achieve this by specifying a query to use for deletion.
To do this, pick the right Analyzer, construct the query, pass the query to the indexWriter to delete the documents.