db.data.group({cond: {'group':'A'},// key: {'group': 1, 'category': 1},keyf:function(doc) {vardt =newDate(doc.created);// or// var dt = doc.datetime;return{year: doc.datetime.getFullYear(),month: doc.datetime.getMonth() +1,day: doc.datetime.getDate() } },initial: {...
Newin version3.6. db.aggregate() Runs a specified admin/diagnostic pipeline which does not require an underlying collection. For aggregations on collection data, seedb.collection.aggregate(). Thedb.aggregate()method has the following syntax: ...
You can execute an aggregation pipeline using the collection.aggregate() method. The following function snippet groups all documents in the purchases collection by their customerId value and aggregates a count of the number of items each customer purchases as well as the total number of purchases ...
In this example, we can use the `$elemMatch` operator to find documents where at least one author has the last name "Smith". Here's how we can do this using the `aggregate` method: ```markdown ```json db.books.aggregate([ { $match: { authors: { $elemMatch: { last_name: "Sm...
3、restore数据到新DB时,不要去先建索引 把bson数据文件restore到另一个DB时,需要注意:不能先创建索引再restore数据,否则性能极差,mongorestore工具默认会在restore完数据时,根据dump出来的index信息创建索引,无须自己创建,如果是要更换索引,也应该在数据入库完之后再创建。
MongoDB\Collection::aggregate()'s returns a MongoDB\Driver\Cursor object. Examples The following aggregation example uses a collection called names and groups the first_name field together, counts the total number of results in each group, and sorts the results by name. <?php $collection = (...
Enable the mixin in your model definition, ieperson.json. {"name":"Person","properties": {"name":"string"},"mixins": {"Aggregate":true} } Usage Invokeaggregatemethod passing either: A regular Loopback filter (where, fields, include, order, skip, limit) ...
MongoDB 2.2 implements much better support for sharded map reduce output. Current Limitations There is a JavaScript lock so a mongod server can only execute one JavaScript function at a point in time .. however, most steps of the MapReduce are very short so locks can be yielded frequently....
EF Core has a change tracking feature. So, you actually don't need to call_issueRepository.UpdateAsync. It will be automatically saved thanks to ABP's Unit Of Work system that automatically callsDbContext.SaveChanges()at the end of the method. However, for MongoDB, you need to explicitly ...
New in 0.7.26 version Added a new annotation CollectionName that can be used on one parameter of an Aggregate2 annotated method to specify the name of the collection on which the aggregate query will be executed. This allows the aggregate query to be specified on the interface method while ...