所以我有一个相当简单的mongo查询,我试图从集合中返回一个唯一年份列表。我有一个使用mongo CLI构建的聚合查询,它返回我正在寻找的结果:
db.rides.aggregate([{'$group': {_id: {year: {'$year': '$date'}}}},{'$sort' : {'_id.year' : -1}}])
当我将此插入使用mongoskin作为db驱动程序的Express应用程序时,会抛出错误
db.collection('rides').aggregate([{'$group': {_id: {year: {'$year': '$date'}}}},{'$sort' : {'_id.year' : -1}}]).toArray(function(err, years) {
res.json(years);
});
错误:
TypeError: Cannot read property 'readPreference' of undefined
at Collection.aggregate (/Users/Shared/projects/fitness-tracker/node_modules/mongoskin/node_modules/mongodb/lib/mongodb/collection/aggregation.js:260:17)
at EventEmitter.<anonymous> (/Users/Shared/projects/fitness-tracker/node_modules/mongoskin/lib/utils.js:120:34)
at EventEmitter.g (events.js:180:16)
at EventEmitter.emit (events.js:98:17)
at /Users/Shared/projects/fitness-tracker/node_modules/mongoskin/lib/utils.js:169:27
at Db.collection (/Users/Shared/projects/fitness-tracker/node_modules/mongoskin/node_modules/mongodb/lib/mongodb/db.js:503:44)
at EventEmitter.<anonymous> (/Users/Shared/projects/fitness-tracker/node_modules/mongoskin/lib/collection.js:51:21)
at EventEmitter.g (events.js:180:16)
at EventEmitter.emit (events.js:98:17)
at /Users/Shared/projects/fitness-tracker/node_modules/mongoskin/lib/utils.js:169:27
我可以找到类似的报告,无法将聚合查询与mongoskin一起使用。不止一些人建议只使用本机mongo驱动程序,但我的堆栈跟踪与我见过的任何东西都不同。我的查询中有什么突出的问题吗?有什么想法吗?
由于
答案 0 :(得分:4)
您的汇总查询syntax
有误,它应该采用callback
函数,如下所示:
db.collection('rides').aggregate([{'$group': {_id: {year: {'$year': '$date'}}}},
{'$sort' : {'_id.year' : -1}}],function(err, years) {
console.log(years);
});
并处理callback
函数中的响应。你可以在那里得到你的结果阵列。