We briefly discussed the importance and general functioning of Indexes in a RAG application in Chapter 3, in the section titled Uncovering the essential building blocks of LlamaIndex – documents, nodes, indexes. Now, it is time to have a closer look at the different indexing methods available in LlamaIndex with their advantages, disadvantages, and specific use cases.

In principle, data can be accessed even without an Index. But it’s like reading a book without a table of contents. As long as it’s about a story that has continuity and can be read sequentially, section by section, and chapter by chapter, reading will be a pleasure. However, things change when we need to quickly search for a specific topic in that book. Without a table of contents, the search process will be slow and cumbersome.

In LlamaIndex, however, Indexes represent more than just a simple table of contents. An Index provides not only the necessary...