本文介绍了环回上的MongoDB聚合的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
如何获取Loopback PersistedModel的总和?
How do I obtain the sum of a Loopback PersistedModel?
关于如何实现该目标,似乎没有文档.
There does not seem to be a documentation on how to achieve that.
如果可能的话,我希望避免查找所有行并将其汇总到Node.js中.
If possible I would like to avoid having to find all the rows and sum it in Node.js.
从 github/strongloop/loopback/issues/890中尝试示例
var bookCollection = Book.getDataSource().connector.collection(Book.modelName);我遇到了错误
throw new Error('MongoDB connection is not established');如何获取集合的句柄以在MongoDB集合上手动运行聚合查询?
How do I get a handle on the collection to manually run aggregate query on a MongoDB collection?
推荐答案最终设法使其正常运行.大多数示例都省略了connect()部分.
Finally managed to get it working. Most examples left out the connect() part.
我的工作代码:
Book.getDataSource().connector.connect(function(err, db) { var collection = db.collection('Book'); var author = Book.getDataSource().ObjectID(authorId); collection.aggregate([ { $match: { authorId: author } }, { $group: { _id: authorId, total: { $sum: "$price" } }} ], function(err, data) { if (err) return callback(err); return callback(null, data); }); });更多推荐
环回上的MongoDB聚合
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