倒排索引 mr实现

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Map阶段

<0,"this is google">

....

context.write("google ->a.txt",1);

context.write("google ->a.txt",1);

context.write("google ->a.txt",1);

context.write("google ->a.txt",1);

context.write("google ->a.txt",1);

context.write("google ->b.txt",1);

context.write("google ->b.txt",1);

context.write("google ->b.txt",1);

--------------------------------------------------------

combiner阶段

<"google ->a.txt",1>

<"google ->a.txt",1>

<"google ->a.txt",1>

<"google ->a.txt",1>

<"google ->a.txt",1>

<"google ->b.txt",1>

<"google ->b.txt",1>

<"google ->b.txt",1>

context.write("google ","a.txt->5");

context.write("google ","b.txt->3");

--------------------------------------------------------

Reducer阶段

<"hello",{"a.txt->5","b.txt->3"}>

context.write("hello","a.txt->5 b.txt->3");

-------------------------------------------------------

hello    "a.txt->5 b.txt->3"

tom        "a.txt->2 b.txt->1"

kitty    "a.txt->1"

.......