如何uid在 pymongo 中使用 map-reduce 找到具有最大字段的文档？
我尝试了以下方法，但它打印出空白：
from pymongo import Connection
from bson.code import Code
db = Connection().map_reduce_example
db.things.insert({
"_id" : "50f5fe8916174763f6217994",
"deu" : "Wie Sie sicher aus der Presse und dem Fernsehen wissen, gab es in Sri Lanka mehrere Bombenexplosionen mit zahlreichen Toten.\n",
"uid" : 13,
"eng" : "You will be aware from the press and television that there have been a number of bomb explosions and killings in Sri Lanka."
})
db.things.insert({
"_id" : "50f5fe8916234y0w3fvhv234",
"deu" : "Ich bin schwanger foo bar.\n",
"uid" : 14,
"eng" : "I am pregnant foobar."
})
db.things.insert({
"_id" : "50f5fe8916234y0w3fvhv234",
"deu" : "barbar schwarz sheep, haben sie any foo\n",
"uid" : 14,
"eng" : "barbar black sheep, have you any foo"
})
m = Code("function () {emit(this.uid,{'uid':this.uid,'eng':this.eng})}")
r = Code("function (key, values) {var total = 0;for (var i = 0; i < values.length; i++) {total += values[i];}return total;}")
result = db.things.inline_map_reduce(m, r)
for r in result:
print
如下所示的示例文档：
{
"_id" : ObjectId("50f5fe8916174763f6217994"),
"deu" : "Wie Sie sicher aus der Presse und dem Fernsehen wissen, gab es mehrere Bombenexplosionen mit zahlreichen Toten.\n",
"uid" : 13,
"eng" : "You will be aware from the press and television that there have been a
number of bomb explosions and killings."
}