Assume that I have a document inside a collection
{
_id: "3434v4vcvc254t34vtds",
currentItemId: "v281",
items: {
v279: [/*Some Data*/],
v280: [/*Some Data*/],
v281: [/*Some Data*/]
}
}
I need to fetch current item.
However I can do it with using two query
let data= await schema.findById("3434v4vcvc254t34vtds", {currentItemId});
let itemId = `items.${data.currentItemId}`
let item = await schema.findByID("3434v4vcvc254t34vtds", { [itemId] })
I need to fetch current item using one query.
Use populate after findById.
const data = await schema.findById('3434v4vcvc254t34vtds').populate('currentItemId').exec()
Related
Hi I tried to update the element at a particular index in an array but I'm not able to update it. It is updating the entire array. Not able to figure out how to update any particular index. Also tried
{$set:{"Data.1:req.body}}
this is updating at 1st index but I don't want to hardcode the index value. It should take from frontend. Let say I have a schema in which I have Data who's type is array and default value is as shown below or anything in the same format.
Data: {
type: Array,
Default: ["0","1","0"]
}
Whenever I'll create a user then Data field will contain these default values, But now I want to update the value at any index (coming from frontend) of Data array of any user created.
I tried findByIdAndUpdate method but I don't know what to pass in set property. If I'm passing this {$set: req.body} and In postman I'm giving any value of Data then obviously it is updating Data array but I want to update value at any index which I'm passing from frontend, let say the index I'm passing is 2 then it should update the value of array at index 2, similarly I can pass any index from frontend how should I do that. What changes I have to make in {$set : } Thanks in advance.
Waiting for any help or suggestions. Thanks
It appears that you can solve this in backend logic if you are passing the index from the frontend.
You can dynamically specify the index, based on the input from the frontend, before you send a query.
const updateUserData = async (req, res) => {
const { index, user_id, new_value } = req.body;
try {
const update = {};
update[`Data.${index}`] = new_value;
const data = await Users.updateOne(
{ _id: user_id },
{ $set: update }
);
return res.status(200).json({ success: true });
} catch (error) {
return res.status(500).json({ success: false });
}
};
I am try to track the number of downloads per click on a website.
server.js
router.post("/download", async (req, res) => {
let id = req.body.id;
id = parseInt(id);
let doc = await db.findOneAndUpdate({_id: id}, {downloads: 100});
});
Note: This works
But I'm trying to increase the number by 1 each time.
For example: Let's say the current number of downloads is 5, how do I do it that if there's a post request. The number of downloads increases by 1.
const { body: { id } } = req;
const intCasetedId = parseInt(id);
const retrievedDocument = await db.findOneAndUpdate({ id }, { $inc: { downloads: 1 } });
A couple things are happening here.
First I get the id value from the the req argument using a destructuring assignment.
I use only const to ensure I do not mutate variable values.
I also use the object property value shorthand notation to skip '_id' key in the search query argument. Quoting mongoose documentation:
Issues a mongodb findAndModify update command by a document's _id field. findByIdAndUpdate(id, ...) is equivalent to findOneAndUpdate({ _id: id }, ...).
Then I am using '$inc' operator to increment the downloads field by 1.
I would also highly recommend for you to research eslint
What is the best approach to do a batch update or transaction, that reads a value of the first update, then uses this value to make further updates?
Here is an example:
//create person
const id = await db
.collection("person")
.add({ ...person })
.then(ref => ref.id)
//then do a series of updates
let batch = db.batch()
const private_doc = db
.collection("person")
.doc(id)
.collection("private")
.doc("data")
batch.set(private_doc, {
last_modified,
version: 1,
versions: []
})
const some_index = db.collection("data").doc("some_index")
batch.update(some_index, {
[id]: { first_name: person.first_name, last_name: person.last_name, last_modified }
})
const another_helpful_doc = db.collection("some_other_collection").doc("another_helpful_doc")
batch.update(another_helpful_doc, {
[id]: { first_name: person.first_name, last_name: person.last_name, image: person.image }
})
return batch.commit().then(() => {
person.id = id
return person
})
You can see here if there is an error any of the batch updates, the person doc will still be created - which is bad. I could add in a catch to delete the person doc if anything fails, however interested to see if this is possible with transactions or batches.
You can call the doc() method, without specifying any path, in order to create a DocumentReference with an auto-generated ID and, then, use the reference later. Note that the document corresponding to the DocumentReference is NOT created.
So, the following would do the trick, since all the writes/updates are included in the batched write:
const new_person_ref = db.collection("person").doc();
const id = new_person_ref.id;
let batch = db.batch()
batch.set(new_person_ref, { ...person })
const private_doc_ref = db // <- note the addition of ref to the variable name, it could help avoiding errors, as this is not a DocumentSnapshot but a DocumentReference.
.collection("person")
.doc(id)
.collection("private")
.doc("data")
batch.set(private_doc_ref, {
last_modified,
version: 1,
versions: []
})
//....
I've a node.js api in which user sends the required fields as an array to be fetched from the mongodb database. I need to find the data of that fields using Find query. I've written forEach statement to loop through that array and got the array elements. But when I try to get the results by inserting the array elements in the query, it doesn't giving the required results. Could any one please help me in resolving the issue by seeing the code below?
templateLevelGraphData: async function(tid,payload){
let err, templateData, respData = [], test, currentValue;
[err,templateData] = await to(Template.findById(tid));
var templateId = templateData.templateId;
payload.variables.forEach(async data=>{
console.log(data); //data has the array elements like variables=["humidity"]
[err, currentValue] = await to(mongoose.connection.db.collection(templateId).find({},{data:1}).sort({"entryDayTime":-1}).limit(1).toArray());
console.log(currentValue);
});
return "success";
}
The expected output is,
[ { humidity: 36 } ]
But I'm getting only _id like,
[ { _id: 5dce3a2df89ab63ee4d95495 } ]
I think data is not applying in the query. But I'm printing the data in the console where it's giving the correct results by displaying the array elements like, humidity. What I need to do to make it work?
When you are passing {data: 1} you are passing an array where is expecting name of column.
You have to create an object where the keys are going to be the elements of the array and set them to 1.
const projection = data.reduce((a,b) => (a[b]=1, a), {});
[...] .find({}, projection) [...]
Actually I got the solution.
for(let i=0;i<payload.variables.length;i++){
var test = '{"'+ payload.variables[i] +'":1,"_id":0}';
var query = JSON.parse(test);
[err, currentValue] = await to(mongoose.connection.db.collection(templateId).find({"deviceId":deviceId},query).sort({"entryDayTime":-1}).limit(1).toArray());
console.log(currentValue); //It's giving the solution
}
I have a user table with some records(such as 100), how can I get one page data and total count from it when there are some where conditions?
I tried the following:
var model = knex.table('users').where('status',1).where('online', 1)
var totalCount = await model.count();
var data = model.offset(0).limit(10).select()
return {
totalCount: totalCount[0]['count']
data: data
}
but I get
{
"totalCount": "11",
"data": [
{
"count": "11"
}
]
}
, how can I get dataList without write where twice? I don't want to do like this:
var totalCount = await knex.table('users').where('status',1).where('online', 1).count();
var data = await knex.table('users').where('status',1).where('online', 1).offset(0).limit(10).select()
return {
totalCount: totalCount[0]['count']
data: data
}
Thank you :)
You probably should use higher level library like Objection.js which has already convenience method for getting pages and total count.
You can do it like this with knex:
// query builder is mutable so when you call method it will change builders internal state
const query = knex('users').where('status',1).where('online', 1);
// by cloning original query you can reuse common parts of the query
const total = await query.clone().count();
const data = await query.clone().offset(0).limit(10);