I am new to mongo. While making a application i came across a weird requirement.
I have collection Document and UserData. The schema for both is given below.
Document {
data : String ,
id : number,
lockedBy : Users
}
Users{
name : String,
email : String,
id : String
}
So here basically a user can lock a document for himself and no one can access it.
The problem here is i dont want to save entire user data in the Document as it will create a lot of redundant data. I want to save the id of the user.
But on the ui side the requirement is to give entire user object(containing id , name , email) as the value of lockedBy.
What I do is i save lockedBy as string with the id of user. Then while fetching i replace the lockedBy with user data by making another call to database and getting the user data based on id.
With increasing number of fetching and saving api i have to make transformation in lot of places. Is there any way to this in a different way. Where i dont have to write the transformation code for lockedBy to change is string to UserData and vice versa.
keep user_id in the Schema,
while sending the response object add users in it, by retrieving it from the the db.
Related
Hello, I have a problem I created a Registration form and im trying to check if there is any user which have a certain username inside the Firebase Db. I tried to get the reference of all the users.
var users = Database.database().reference("users")
But I don't know how I could check if there is any user with a specified username.
You'll want to use a query for that. Something like:
let query = users.queryOrdered(byChild: "username").equalTo("two")
Then execute the query and check whether the result snapshot exists.
Note though that you won't be able to guarantee uniqueness in this way. If multiple users perform the check at the same time, they may both end up claiming the same user name.
To guarantee a unique user name, you will need to store the user names as the key - as keys are by definition unique within their parent node. For more on this, see some of these top search results and possibly also from here.
I'm trying to set up a webpage that communicates with a Moodle page. I need different data from a database activity and want to create new entries. Note that I am not talking about the SQL database in BG, it is the activity database in courses.
The information should be retrieved/transferred via the REST API, an HTML POST Request. My problem is that I don't know how to add a new record to the database activity because I cannot transfer the data array. Only the first parameter given appears in my database.
E.g. i tried ...&wsfunction=mod_data_add_entry&databaseid=10&data[0][fieldid]=66&data[0][value]=12&data[1][fieldid]=67&data[1][value]=test
And many other combinations. Always only the first parameter is shown in the database.
The docs tell me this (Pseudocode):
//The fields data to be created
list of (
object {
fieldid int //The field id.
subfield string Default to "" //The subfield name (if required).
value string //The contents for the field always JSON encoded.
}
)
Alternatively:
REST (POST parameters)
data[0][fieldid]= int
data[0][subfield]= string
data[0][value]= string
I cannot find anywhere else something called a "subfield".
Any ideas?
Okay, found it. You have to put your values in "", unless they are not a number. Seems like there is a connection with this special activity because you don't have to do it elsewhere.
How can I get the document id of a collection present in the cloud Firestore?
I tried to get it by using the
firebase.firestore().collection("collectionName").doc().id
but I didn't get the appropriate result.
firebase.firestore().collection("societies").doc().id and it returns a id which is not equivalent to society documentId
That's correct because everytime when you are using the above line of code, you are generating a new document id which will never be the same with one that already exist in your database.
In order to use a new document id, first you need to generate it (as you already do) and then store it in a variable. Having that varaible which holds that id, you can use it to get that particular document from the database by passing this id as an argument to the doc(id) function:
firebase.firestore().collection("societies").doc(this.myId)
I am using mongodb and odata.
I want to select name field alone for particular user id. (i.e) select name from userdata where userid=1;
/*my collection schema - userdata*/
{
id:number,
userid:string,
name:string,
data:object
}
I tried http://localhost:27017/userdata?$format=json&$filter=userid eq '1'&$select=name
Instead of getting name file alone I got whole object/document that matches userid=1. What I am doing wrong here?
I spoted the problem after the comment from #jps.
The issue is not with query, the problem is with data model which I am using is mismatching with my database schema (i.e) I missed out name field in model, so it is returning whole collection.
Now model is fixed, so the service is responding back with names for given userid.
What is the correct way of storing large lists in PostgreSQL?
I currently have a "user" table, where the "followers" column stores a list of the followers that that user has. This list is stored in JSON, and every time the server wants to add a new user to that list, it retrieves it from the database, appends the new user, and then replaces the old list with the new list.
The problem is that these lists tend to get quite lengthy, which might affect performance. Is it possible to simply append to the list directly via SQL without retrieving it and rewriting it later?
Use a separate table for followers. The table should have at least two columns: userid and followerid. And it's good practice to have a primary key for this table as well, so let's give it a "ufid".
You can do a select to get all the elements and compute the JSON string if your application needs it. But do not work with JSON or any other string representation of the list, as it defeats the purpose of a relational database.
To add a new follower, simply add a new record to the follower table with the userid; deleting and update are also done on the record level without working with the "other records".
If followers is a list of integers which are primary keys to their accounts, make it an integer array int[]. If they are usernames or other words, go with a string array character varying[].
To append to an array column you can do this:
UPDATE the_table SET followers = followers || new_follower WHERE id = user;