MongooseError: Query was already executed - node.js

Question

I updated Mongoose to the latest version (6.0.1) and now I'm getting this error whenever .findOne() is executed:
MongooseError: Query was already executed: Streams.findOne({ i: 6 })
at model.Query._wrappedThunk [as _findOne] (C:\Users\honza\ZiggerTestMaster\node_modules\mongoose\lib\helpers\query\wrapThunk.js:21:19)
at C:\Users\honza\ZiggerTestMaster\node_modules\kareem\index.js:370:33
at processTicksAndRejections (node:internal/process/task_queues:78:11)
at runNextTicks (node:internal/process/task_queues:65:3)
at listOnTimeout (node:internal/timers:526:9)
at processTimers (node:internal/timers:500:7) {
originalStack: 'Error\n' +
' at model.Query._wrappedThunk [as _findOne] (C:\\Users\\honza\\ZiggerTestMaster\\node_modules\\mongoose\\lib\\helpers\\query\\wrapThunk.js:25:28)\n' +
' at C:\\Users\\honza\\ZiggerTestMaster\\node_modules\\kareem\\index.js:370:33\n' +
' at processTicksAndRejections (node:internal/process/task_queues:78:11)\n' +
' at runNextTicks (node:internal/process/task_queues:65:3)\n' +
' at listOnTimeout (node:internal/timers:526:9)\n' +
' at processTimers (node:internal/timers:500:7)'
}
My code is as follows:
var visitorData = Visitor.find({});
app.get("/retrieve", function(req,res){
visitorData.exec(function (err,data) {
if (err) {
throw err;
}
res.render("retrieve", { title:"View Visitor Data", records: data});
});
});
It executes properly the first time I open the route but, whenever I refresh it, it throws the above error. Has been happening since Mongoose got the latest version.

Answer 1

Had the same issues, but the release notes on mongoose helped, I chained a .clone() method to the .find() method:
https://mongoosejs.com/docs/migrating_to_6.html#duplicate-query-execution
Mongoose no longer allows executing the same query object twice. If
you do, you'll get a Query was already executed error. Executing the
same query instance twice is typically indicative of mixing callbacks
and promises, but if you need to execute the same query twice, you can
call Query#clone() to clone the query and re-execute it.
So all you need to do is to add a .clone() method to the end of the mongoose method that needs to be called concurrently like below (I restructured your code a bit):
app.get("/retrieve", function (req, res) {
Visitor.find({}, function (err, data) {
if (!err) {
res.render("retrieve", { title: "View Visitor Data", records: data });
} else {
throw err;
}
}).clone().catch(function(err){ console.log(err)})
});

Answer 2

wrap your query within async-await.
const visitorData = async() => {
return await Visitor.find({});
}

Answer 3

Don't use the callback within the findOne, instead
use .then() , after the Query, like so
Visitor.find({})
.then(function (err, data) {
if (!err) {
res.render("retrieve", { title: "View Visitor Data", records: data });
} else {
throw err;
}
}
This should most likely work , otherwise use clone() if necessary , as stated by
Avis

Answer 4

The error predominantly arises because the same query is executed more than once, the most often cause being unknowingly using promise and callback at the same time, to avoid such mistakes this error is thrown.
To get rid of this error, stick to either promise or callback when executing this query method.
Use:
await Model.findOneAndUpdate(query,doc,options)
// (or) regular .then() .catch() syntax
Model.findOneAndUpdate(query)
.then(res=>...)
.catch(err=>...)
(OR)
Model.findOneAndUpdate(query, doc, options, callback)
The same principle applies to similar methods like findByIdAndUpdate.

Answer 5

Mongoose v6 does not allow duplicate queries.
Mongoose no longer allows executing the same query object twice. If you do, you'll get a Query was already executed error. Executing the same query instance twice is typically indicative of mixing callbacks and promises, but if you need to execute the same query twice, you can call Query#clone() to clone the query and re-execute it. See gh-7398
Duplicate Query Execution
In my case, I assumed my Apollo Server resolver will wait for the promise to resolve and return the result, but that wasn't the case. So I had to add async/await to the mongoose query.

Answer 6

I'm not sure about the details but mine and my co-workers problems got fixed by downgrading mongoose to 5.13.14

Answer 7

Mongoose no longer allows executing the same query object twice. If you do, you'll get a Query was already executed error. Executing the same query instance twice is typically indicative of mixing callbacks and promises, but if you need to execute the same query twice, you can call ".clone();" to clone the query and re-execute it.

Answer 8

// Mongoose 6.6.3
// Query.prototype.clone()
// Returns:
// «Query» copy
// Make a copy of this query so you can re-execute it.
// Example:`enter code here`
const q = Book.findOne({ title: 'Casino Royale' });
await q.exec();
await q.exec();
// Throws an error because you can't execute a query
twice
await q.clone().exec(); // Works

Answer 9

My mistake was using find() for finding a record like this:
foo.find(a=> a.id === id) //It is wrong!
It should be:
foo.findById(id)

Answer 10

The newer version of Mongoose (version 6+) doesn't support executing the same query object twice. So, just downgrade to an older version, like version 5.13.15.
Uninstall the current Mongoose package & then download the older version:
npm uninstall mongoose
npm i mongoose#5
Hope, this can resolve the issue.