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Can I utilize indexes when querying by MongoDB subdocument without known field names?
<p>Yes, you can achieve this by indexing like “properties.k” for key and “properties.v” for value. The same is used to be implemented in ensureIndex().</p><p>Let us first see an example and create a collection with documents −</p><pre class="prettyprint notranslate">> db.demo274.insertOne({"details":[{StudentFirstName:"Chris",StudentLastName:"Brown"}, ... {StudentFirstName:"David",StudentLastName:"Miller"}, ... {StudentFirstName:"John",StudentLastName:"Smith"}, ... {StudentFirstName:"John",StudentLastName:"Doe"} ...] ...} ...); { "acknowledged" : true, "insertedId" : ObjectId("5e48de35dd099650a5401a42") }</pre><p>Display all documents from a collection with the help of find() method −</p><pre class="prettyprint notranslate">> db.demo274.find().pretty();</pre><h2>Output</h2><p>This will produce the following output −</p><pre class="result notranslate">{ "_id" : ObjectId("5e48de35dd099650a5401a42"), "details" : [ { "StudentFirstName" : "Chris", "StudentLastName" : "Brown" }, { "StudentFirstName" : "David", "StudentLastName" : "Miller" }, { "StudentFirstName" : "John", "StudentLastName" : "Smith" }, { "StudentFirstName" : "John", "StudentLastName" : "Doe" } ] }</pre><p>Following is the query to utilize indexes when querying by MongoDB subdocument without known field names −</p><pre class="prettyprint notranslate">> db.demo274.ensureIndex({"details.StudentFirstName": 1, "details.StudentLastName": 1});</pre><h2>Output</h2><p>This will produce the following output −</p><pre class="result notranslate">{ "createdCollectionAutomatically" : false, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }</pre>
Updated on 31-Mar-2020 13:10:51
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