Note that this only returns the first match for each document: if Bob had left multiple comments on this post, only the first one in the "comments" array would be returned. Array and range query interactions Scalars (non-array elements) in documents must match each clause of a query’s ...
array. Thesemultikey indexesallow queries to select documents that contain arrays by matching on element or elements of the arrays. MongoDB automatically determines whether to create a multikey index if the indexed field contains an array value; you do not need to explicitly specify the multikey...
If your query patterns require accessing individual array elements, use a multi-key index. MongoDB creates an index key for each element in the array and can be constructed over arrays that hold both scalar values and nested documents. Avoid Regular Expressions That Are Not Left Anchored or Roo...
The $elemMatch operator limits the contents of an <array> field from the query results to contain only the first element matching the $elemMatch condition. $elemMatch操作符将查询结果中的<array>字段的内容限制为仅包含与$elemMatch条件匹配的第一个元素。 { _id: 1, zipcode: "63109", students: ...
The $elemMatch operator limits the contents of an <array> field from the query results to contain only the first element matching the $elemMatch condition. $meta 在$meta每个匹配文档投影算子返回元数据(例如"textScore")与所述查询相关联。
return this; } } //用于匹配正则表达式 private boolean lastOperatorWasNot() { return !this.criteria.isEmpty() && "$not".equals(this.criteria.keySet().toArray()[this.criteria.size() - 1]); } //不等于 public Criteria ne(@Nullable Object o) { this.criteria.put("$ne", o); return ...
For example, you may want to check whether certain elements of some massive nested arrays exist. To do this, we can use array indexing syntax in MQL. For instance, to find the races with only one sponsor, we need to check whether the second element of the sponsors array exists: # ...
These multikey indexes allow queries to select documents that contain arrays by matching on element or elements of the arrays. MongoDB automatically determines whether to create a multikey index if the indexed field contains an array value; you do not need to explicitly specify the multikey type...
the substring 'ar' using a regular expressiondb.find({planet:/ar/},function(err,docs){// docs contains Mars and Earth});// Finding all inhabited planets in the solar systemdb.find({system:'solar',inhabited:true},function(err,docs){// docs is an array containing document Earth only});...
Match an Array Value If the specified<value>is an array, MongoDB matches documents where the<field>matches the array exactly or the<field>contains an element that matches the array exactly. The order of the elements matters. For an example, seeEquals an Array Value. ...