Text search question about implementation

Can someone explain me how the text searching algorithm works? I understand its a huge field but am trying to understand it from high level so that I can look up academic papers on it. For example, Spelling mistakes is one problem that is tough to solve and of course Google solves it. When I search for a term and misspell it on Google, it automatically suggests th开发者_开发问答e correct spelling. How is indexing done for it? Using MapReduce I can see they index various entities. What do they or some one else index and store? May be I am looking for a practical implementation of MapReduce if I am thinking in the right direction at all.

• Pav

I'm afraid this question really is too big, which probably explains why it has not seen an answer yet. As far as Google's spell-checker is concerned, Peter Norvig explains how it is done: How to Write a Spelling Corrector

The exact implementation in productive use at Google surely looks quite a bit different and way more complicated, but this might get you started.