The next design patterns we're going to discuss, are
summarization patterns. And, these are patterns that give you, some
quick easy high level understanding of your data. And we're
going to make a distinction here. We're going to talk about making
what's called an inverted index. And this is very similar
to the index you'd find in a back of a
book, or the indexing that Google does when it crawls
the web. And, we're also going to talk about numerical summarizations.
And, these are things like finding counts, how many of a certain record type, or
min and max. And min and max of course, can be used to calculate first
or last. Or calculate statistics like, mean
and median, and basically any other high level
numerical value that you can use to summarize
your data set. In this section of summarization
patterns, we'll also talk about some
interesting additional [INAUDIBLE] functionality, something that
can exist between [INAUDIBLE] reducers, known
as combiners. So, let's keep going.