MongoDB offers various methods for counting the documents in a collection or view. There are also some aggregation operators that enable you to count incoming documents from a previous aggregation pipeline stage.
Continue readingCategory: MongoDB
MongoDB $sampleRate
In MongoDB, the $sampleRate aggregation pipeline stage matches a random selection of input documents.
The number of documents selected approximates the sample rate expressed as a percentage of the total number of documents.
The $sampleRate operator was introduced in MongoDB 4.4.2.
MongoDB $reverseArray
In MongoDB, the $reverseArray aggregation pipeline operator reverses the order of items in an array.
It accepts an array expression as an argument and returns an array with the elements in reverse order.
Continue readingMongoDB $range
In MongoDB, the $range aggregation pipeline operator returns a generated sequence of numbers in an array.
This sequence of numbers is based on the input values you provide.
Continue readingMongoDB $round
In MongoDB, the $round aggregation pipeline operator rounds a number to a whole integer or to a specified decimal place.
You have the option of specifying how many decimal places for which to round the number. To do this, pass a second argument. The first argument is the number to round, and the second (optional) argument is the number of decimal places to round it to.
Continue readingImport Documents into MongoDB from an Array of JSON Documents
When using mongoimport, you can use the --jsonArray parameter to import an array of JSON documents.
Find Out if a Query uses an Index in MongoDB
In MongoDB, you can use the cursor.explain() method or the db.collection.explain() method to determine whether or not a query uses an index.
These methods enable you to view the query plan for the query, which includes whether or not it uses an index.
Continue readingMongoDB $sample
In MongoDB, the $sample aggregation pipeline stage randomly selects the specified number of documents from its input.
MongoDB $rand
In MongoDB, the $rand aggregation pipeline operator returns a random float between 0 and 1.
The floating point value has up to 17 digits after the decimal point. Any trailing zeros are dropped, so the number of digits may vary.
The $rand operator was introduced in MongoDB 4.4.2.
MongoDB $nin Query Operator
In MongoDB, the $nin query operator selects the documents where the field’s value is not in the specified array or where the field doesn’t exist.