如何在搜索引擎的数据库中存储文档向量?

I have implemented a search engine in Java. It has a database that stores the inverted index ie mapping from terms to list of documents the term appears in. There is a feature that allows a user to upload a document which can be added to document for indexing. The problem that i'm facing is that , everytime a new document is added , the index is reconstructed in memory instead of being updated . To update , i would need a database that stores document vectors that are essentially tf-idf's(term frequency* inverse document frequency) of each and every term in the index. I'm not able to work out database structure for it as in what rows and columns or multiple tables would be needed for storing such a structure.I have implemented a search engine in Java. It