Have you ever wondered how Google returns a search result in less than a second? It’s all made possible through the magic of indexing. On periodic basis, Google will go out across the Internet and crawl all of the content that it can access. During this process, the crawler pulls each and every document, webpage, or whatever, back to the indexer, were the document is broken down into the list of words it contains. Google creates a database which in the world of search is often called the index. When a user executes a query, the index is what is queried for relevant data resulting is sub-second response time. Think of an index as a data warehouse for unstructured information.
Now all of this sounds great, but there are times, when indexing information is not appropriate or even possible.