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Solving the Issue: Why Your Mongoose MongoDB Push Isn't Working

Discover how to effectively use `$addToSet` in Mongoose to manage arrays in MongoDB, ensuring unique entries and avoiding push operation failures. --- This video is based on the question https://stackoverflow.com/q/75058831/ asked by the user 'MIike Eps' ( https://stackoverflow.com/u/12072045/ ) and on the answer https://stackoverflow.com/a/75069580/ provided by the user 'Mandeep' ( https://stackoverflow.com/u/14604327/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: user updates using Mongoose mongodb push not working Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Solving the Issue: Why Your Mongoose MongoDB Push Isn't Working When working with MongoDB and Mongoose in your Node.js applications, you might encounter scenarios where updating an entity to push an item into an array fails silently. A common complaint is the update operation returning a confirmation of "acknowledged: true" but having a "modifiedCount" of zero. If you're facing this issue, you're not alone, and this guide is here to help! Understanding the Problem In the specific case we are addressing, a user needed to update an entity's dcrLocations array to include a new dcrLocationId. However, despite the operation being acknowledged, the relevant entry was not added to the database, resulting in: [[See Video to Reveal this Text or Code Snippet]] The Likely Causes No Matching User Found: The operation may not have matched any user due to an incorrect user ID (req.params.id). Using $push Instead of $addToSet: If the item you’re trying to push already exists in the array, $push will not update it because it allows duplicates, but you want distinct entries. The Solution: Use $addToSet Instead of using $push, use $addToSet. This operator adds a value to an array only if the value does not already exist, which is especially useful when you want to avoid duplicates. Here’s how you can implement it. Step-by-Step Implementation Below is the revised code using $addToSet: [[See Video to Reveal this Text or Code Snippet]] Key Changes Explained Using $addToSet: The change from $push to $addToSet ensures that only unique entries are added, which is essential in preventing issues of duplicates in your dcrLocations array. Preserving ObjectID: The dcrLocationId is still wrapped in new ObjectId(dcrLocationId), ensuring that MongoDB recognizes it as an ObjectId. Conclusion By switching from $push to $addToSet, you ensure that your updates to arrays are both efficient and effective. This small change is critical in managing unique entries in your MongoDB collections, leading to a cleaner and more reliable database operation. If you find yourself troubleshooting similar issues in Mongoose or any other MongoDB-related challenges, consider these insights to enhance your coding practices. Happy coding!