We don't have 2000 apache tutorials any more in the index, so they will do something like that.
a 100% identical text needs just one check, similar as you do in your G search. Then the text will be checked further (Guess obviously).
Somewhat similar text might be checked in a different way,checksums and so on. One word query 0.13 seconds, 6 word query 0.10 seconds in your G search.
Very rough extimate:
Lets say 1.000.000.000 pages search on each 0.1 seconds = 100000000 seconds, split on 1000 servers = 100000 seconds = 27.78 hours, feasable, and if they have more servers that time is reduced + higher PR gets more attention and if you have a 9 word search string matched on 40 other pages that page might get dumped immediately. IE apache docu or all the news that were replicated on 100 pages in the past. There are ways to reduce what needs to be investigated.