If you get the “$pullAll requires an array argument but was given a double” error in MongoDB, it’s because you didn’t provide an array as the value to replace.
MongoDB
How to Format the Date in MongoDB
If you have documents that store dates as Date objects, but you want to return them in a different format, you can use the $dateToString aggregate pipeline operator.
For example, you might want a date to be returned in mm/dd/yyyy format instead of the long ISODate() format that includes minutes, seconds, milliseconds, etc
The $dateToString operator converts the Date object to a string, and optionally allows you to specify a format for the resulting output.
Fix “longitude/latitude is out of bounds” in MongoDB when Creating a 2dsphere Index
If you’re getting a “longitude/latitude is out of bounds” error when trying to create a 2dsphere index in MongoDB, it could be due to your longitude and latitude coordinates being in the wrong order.
How to Check Whether an Index is Hidden in MongoDB
From MongoDB 4.4, it’s possible to hide an index from the query planner. This allows you to evaluate the potential impact of dropping an index without actually dropping the index.
You can use the getIndexes() method to check whether or not an index is hidden. If an index is hidden, that index will display a hidden field as having a value of true (i.e. "hidden" : true).
3 Ways to Hide an Index from the Query Plan in MongoDB
Starting from MongoDB 4.4, we can now hide indexes from the query plan. This enables us to evaluate the potential impact of dropping an index without actually dropping the index.
If hiding it has a negative impact, we can unhide the index. This saves us from having to drop the index, then recreate it again.
Below are 3 ways to hide an index in MongoDB.
3 Ways to Return Distinct Values in MongoDB
Distinct values are those values with redundant duplicates removed. In other words, distinct values are unique values.
In MongoDB there are a few ways we can return distinct values in a query. This article presents 3 ways to return distinct values in the mongo shell.
3 Ways to Drop an Index in MongoDB
MongoDB provides several ways to drop an index or indexes.
To drop a single index, you can use the dropIndex() method.
To drop multiple indexes, you can use either the dropIndexes() method or the dropIndexes administration command.
MongoDB sort()
In MongoDB, the cursor.sort() method specifies the order in which the query returns matching documents.
The sort() method accepts a document that specifies the field to sort, and the sort order. The sort order can be either 1 for ascending or -1 for descending.
You can also specify { $meta: "textScore" } when doing $text searches, in order to sort by the computed textScore metadata in descending order.
MongoDB $orderBy
In MongoDB, the $orderBy query modifier sorts the results of a query in ascending or descending order.
$orderBy accepts a document that specifies the field to sort, and the sort order. The sort order can be either 1 for ascending or -1 for descending.
$orderBy has been deprecated in the mongo shell since v3.2. Use the cursor.sort() method instead.
MongoDB $sort
In MongoDB, the $sort aggregation pipeline stage sorts all input documents and returns them to the pipeline in sorted order.