[英]mongodb mapreduce scope - ReferenceError
I'm trying to use an external object inside mongodb map/reduce functions. 我试图在mongodb map / reduce函数中使用外部对象。 If the object has a variable which it should access, an error occurs.
如果对象具有应访问的变量,则会发生错误。
For example: 例如:
var conn = new Mongo();
var db = conn.getDB("test");
var HelperClass = function() {
var v = [1, 2, 3];
this.data = function() {
return v;
};
};
var helper = new HelperClass();
var map = function() {
helper.data().forEach(function(value) {
emit(value, 1);
});
};
var reduce = function(key, values) {
var count = 0;
values.forEach(function(entry) {
count += entry;
});
return count;
};
db.test.mapReduce(map, reduce, {
out: "temp",
scope: {
helper: helper
}
});
The output from mongodb: mongodb的输出:
map reduce failed:{ "errmsg" : "exception: ReferenceError: v is not defined", "code" : 16722, "ok" : 0 } at src/mongo/shell/collection.js:970
映射减少失败:{“ errmsg”:“例外:ReferenceError:未定义v”,“代码”:16722,“确定”:0},位于src / mongo / shell / collection.js:970
Is it an expected behavior? 这是预期的行为吗? Is there any other way to use external objects in mapReduce?
在mapReduce中还有其他使用外部对象的方法吗?
What's casuing the problem is this function: 造成此问题的原因是此功能:
var HelperClass = function() {
var v = [1, 2, 3];
this.data = function() {
return v.data;
};
};
Since: 以来:
return v.data;
Is in a different scope to the real variable which is actually this.v.data
. 与实际变量
this.v.data
范围不同。
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