mongodb：未知的分片 m/r 字段：限制
当我在mapreduce分片集合中使用“limit”时，我看到这个错误： unknown m/r field for sharding: limit
Code:
m = function() { emit(this.user_id, 1); }
r = function(k,vals) {
var sum=0;
for(var i in vals) sum += vals[i];
return sum;
}
db.visits.mapReduce(m, r,{out: { inline : 1}, limit: 4});
I use mongodb 2.0.2
昨天我有 2具有分片和“限制”参数的服务器工作正常，但今天我又添加了 2 个服务器，设置了一个新的分片并遇到了这个问题。
When I use "limit" in mapreduce sharding collection I see this error: unknown m/r field for sharding: limit
Code:
m = function() { emit(this.user_id, 1); }
r = function(k,vals) {
var sum=0;
for(var i in vals) sum += vals[i];
return sum;
}
db.visits.mapReduce(m, r,{out: { inline : 1}, limit: 4});
I use mongodb 2.0.2
Yesterday I had 2 servers with sharding and "limit" paramenter worked fine but today I've added 2 more servers, setup a new sharding and got this problem.
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分片映射缩减目前不支持
limit选项：https://jira.mongodb.org/browse/SERVER-2099
我不是确定它会如何对抗两个碎片。它不应该有，除非您直接连接到单个分片。
The
limitoption is currently unsupported for sharded map-reduce:https://jira.mongodb.org/browse/SERVER-2099
I'm not sure how it would have worked against just two shards. It shouldn't have, unless you were connecting directly to a single shard.