I am creating task entries by Firestore User.ID or UID..For every new User.ID collection...i get an error message that says a index has to be created by that particular User.ID which is not feasible given that in my solution i can have any number of users...cannot be running back to create an index for each user
Individual Index by UserID
Trying desperately to find a solution...i thought right or otherwise that i have to create a Single Field Exemption for User.UID...which i did as shown below BUT it does not work....My query is by User.ID on the field priority.....What is worse...i now cannot delete that Single Field Exemption...when i click on it...it is highlighted but no menu option appears...
Single Field Exemption
Any idea how to delete it and more importantly how to not have to create an index for each User.ID...As normal...Googles documentation is totally useless .....it does not answer to specific situations.
Affected Entries
Example Affected Entries
When an authenticated user enters a task document...it records their UUID as a new entry (marked in RED) and associated documents...Every time a new entry is made for a new user....it is not updated but an error message is obtained that says index needs to be created ..the index id is the user UID. It asks for every new user...
Related
I want to assign a unique but incremental document/record(a data entry, not Firebase document) number when user generates his/her document in the app.
The document number should be unique integer/long and will be visible on the generated PDF document of the user as Your document number : 1100xxxxxx. This last generate document's number will be stored separately so when a new user generated his/her document, this number can be easily picked, incremented and assigned to user.
This way I won't have to query the database again for the last generated number using sorting as
FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
Query query = rootRef.collection("Users")
.orderBy("DocumentNo", Query.Direction.DESCENDING)
.limit(1);
Right now, I generate a user by assigning the user.uid to the Firebase document. The reason I want to ensure the uniqueness of generated certificate number is that it will be visible to user and multiple users will be hitting the server at the same time(same millisecond even).
Although, I've seen almost every similar answer but the answer I've found similar to what I was thinking is this. Also, this unanswered question is what I should do but it has problems too.
So, is there a way by which I can generate a unique document/record number to the user? Answer need not be in Flutter, I want the logic mainly.
If you want to increment a number every time something happens do:
document.ref.update({unique_value: FieldValue.increment(1)});
That number will be unique. It will work with multiple users hitting the server at the same time.
I am creating a leave tracker app where I want to store the user ID along with the from date and to date. I am using Amazon's DynamoDB as the database, and the user enters a leave through a custom command.
Eg: apply-leave from-date to-date
I want to avoid duplicate entries in the database. For example, if a user has already applied for a leave between 06-10-2019 to 10-10-2019 and applies for a leave between the same dates again, they should get a message saying that this already exists and a new record should not be created for the same.
However, a user can apply for multiple leaves and two users can take a leave between the same dates.
I tried using a conditional statement as follows:
table.put_item(
Item={
'leave_id': leave_id,
'user_id': user_id,
'from_date': from_date,
'to_date': to_date,
},
ConditionExpression='attribute_not_exists(user_id) AND attribute_not_exists(from_date) AND attribute_not_exists(to_date)'
)
where leave_id is the partition key. However, this does not work and a new row is added every time, even if it is the same dates. I have looked through similar other questions, but haven't been able to understand how to get this configured correctly.
Any ideas on how I should go about this, or if there is a different design that I should follow?
If you are calling your code with the leave_id that doesn't yet exist in the table, the item will always be inserted. If you call your code with leave_id that does already exist in your table you should be getting An error occurred (ConditionalCheckFailedException) when calling the PutItem operation: The conditional request failed error message.
I have two suggestions:
If you don't want to change your table, you can create a secondary index with user_id as the partition key and then query the index for all the items where the given user has some from_date and to_date attributes.
Like this:
table.query(
IndexName='user_id-index',
KeyConditionExpression=Key('user_id').eq(user_id),
FilterExpression=Attr('from_date').exists() & Attr('from_date').exists()
)
Then you will need to check for overlapping leave requests, etc. (eg. leave request that starts before the one that is already in place finishes). After deciding that the leave request is a valid one you will call put_item.
Another suggestion and probably a better one would be to create a composite primary key on your table with user_id as a partition key and leave_id as a sort key. That way you could execute a query for all leave requests from a particular user without the need to create a secondary index.
Am looking at the data structure in this post and want to know how you would go about getting the emails of users who belong to a certain group when they could belong to several groups and the GroupID stored against that user is the current group they are participating in?
Do you store the email addresses with the userid under the "members" or, instead, for each member of the group, get that user's email address from the "users" document userid (this would mean iterating through the group/members collection and doing a query for each user. Not very efficient).
Am used to SQL so this is all new to me.
You should have a single node for each user
/users/UID/emails/
/users/UID/emailunread/
/users/UID/settings/
/users/UID/details/
/users/UID/payments/
So you can simply do a subscription for a singular node path this.myDatasubscription = this.DB.list('users/' + this.uid).snapshotChanges() ensuring changes like new emails or account settings will detected and rolled out in real time back to the app, so your are using angular/ng or something similar client side then your variables {{this.email_list}} should update real time with no page changes.
Take a look at this one.
error: Property 'getChildren' does not exist on type 'DataSnapshot'
I'm working on a website that mostly displays items created by registered users. So I'd say 95% of API calls are to read a single item and 5% are to store a single item. System is designed with AWS API Gateway that calls AWS Lambda function which manipulates data in DynamoDB.
My next step is to implement voting system (upvote/downvote) with basic fetaures:
Each registered user can vote only once per item, and later is only allowed to change that vote.
number of votes needs to be displayed to all users next to every item.
items have only single-item views, and are (almost) never displayed in a list view.
only list view I need is "top 100 items by votes" but it is ok to calculate this once per day and serve cached version
My goal is to design a database/lambda to minimize costs of AWS. It's easy to make the logic work but I'm not sure if my solution is the optimal one:
My items table currently has hashkey slug and sortkey version
I created items-votes table with hashkey slug and sortkey user and also voted field (containing -1 or 1)
I added field votes to items table
API call to upvote/downvote inserts to item-votes table but before checks constraints that user has not already voted that way. Then in second query updates items table with updated votes count. (so 1 API call and 2 db queries)
old API call to show an item stays the same but grabs new votes count too (1 API call and 1 db query)
I was wondering if this can be done even better with avoiding new items-votes table and storing user votes inside items table? It looks like it is possible to save one query that way, and half the lambda execution time but I'm worried it might make that table too big/complex. Each user field is a 10 chars user ID so if item gets thousands of votes I'm not sure how Lambda/DynamoDB will behave compared to original solution.
I don't expect thousands of votes any time soon, but it is not impossible to happen to a few items and I'd like to avoid situation where I need to migrate to different solution in the near future.
I would suggest to have a SET DynamoDB (i.e. SS) attribute to maintain the list of users who voted against the item. Something like below:-
upvotes : ['user1', 'user2']
downvotes : ['user1', 'user2']
When you update the votes using UpdateExpression, you can use ADD operator which adds users to SET only if it doesn't exists.
ADD - Adds the specified value to the item, if the attribute does not
already exist. If the attribute does exist, then the behavior of ADD
depends on the data type of the attribute:
If the existing data type is a set and if Value is also a set, then
Value is added to the existing set. For example, if the attribute
value is the set [1,2], and the ADD action specified [3], then the
final attribute value is [1,2,3]. An error occurs if an ADD action is
specified for a set attribute and the attribute type specified does
not match the existing set type. Both sets must have the same
primitive data type. For example, if the existing data type is a set
of strings, the Value must also be a set of strings.
This way you don't need to check whether the user already upvote or downvote for the item or not.
Only thing you may need to ensure is that the same user shouldn't be present on upvote and downvote set. Probably, you can use REMOVE or ConditionExpression to achieve this.
if one user accessing the record 1 out of 10 records in a table. if at the same time, 2nd user trying to access that same record of 1st user, he should not be displayed that record but instead he should be displayed 2nd record and because this first user will be holding the record for some time to process and update till then this records should not be shown to any other user even select query is fired from second user application. is it possible using Row Lock? please provide me the example how to implement rowlock and holdlock and release the hold lock used Row level lock. apart from this if you have any other suggestion please share it
I am using SqlServer2005 with Asp.Net
Babu.M
I don't know if row lock would stop it being selected but could you not use a audit table? For example when user one gets access to the record store the ID for that record in an audit table and then when user two trys to use a record the application should check to see if the primary key for the record is in the audit table, if it is the second user does not gain access if not the second user gains access. Once a user has finished with the record you can either delete the record in th audit table or you could keep the record but set a flag to say it is no longer in use as this way you could see who has changed what record and at what time if you add a date time stamp.
Again when using select command just make it so that if the primary key is present in the audit table you don't select it.
Hope this helps