Till now, I have coded apps which load listviews completely from web(parsing,etc) or completely from local database. What I intend to develop is a listview which will load from existing local database, and check the web database and fetch only those entries which do not exist in the local cache, and then update the local cache with those new entries.
I had a naive idea of implementing it. There would be a single value in local data about the number of entries in local database. Similarly, there would be a value of number of entries on the web database. Then we can exactly fetch the required number of entries from the web, instead of fetching the entire list again.
Is there some better/easier way to do it?
I found a solution to this. The better thing to do would be to do this checking on a middle layer server. It would be like a 3 layer application. There would be a middle layer which would store all the posts seen by the current user. So next time user wants to update himself, the middle layer can check what results were posted back to him last time
Related
I have search a lot on stackoverflow and read many questions
I was having 3 indexOn problem 2 of them are solved and 1 remains
I am sorting database and have indexOn on "favorite" and "poet" which runs successfully but I need one more indexOn for numbers inside heart node.
query is running successfully but I am getting indexOn warning in android studio
I have tried using variables in place of numbers in database rule but still getting warning
Using an unspecified index. Your data will be downloaded and filtered on the client. Consider adding '".indexOn": "heart/+91916*******"' at gazal to your security and Firebase Database rules for better performance
queryFav = FirebaseDatabase.getInstance()
.getReference(reference).orderByChild(child).equalTo("heart");
above query run successfully but what should be indexOn rule
The message you get means you are running a query that has orderBy("heart/+91916*******") on a node named gazal. To efficiently run that query, you need to have an index on heart/+91916******* to that node in your security rules. But since the +91916******* part of that index probably is dynamic (i.e. you'll have a different value of +91916******* for every user of the app), you'll have to add an index for each user. That is not feasible.
In other words: you current data structure makes it easy to read the users who have hearted a specific poem. It does however not make it easy to determine the poems that a specific user has hearted. To make that equally easy, you'll want to add an additional data structure"
"user_hearts": {
"+91916*******": {
"-KjYiXzl1ancR8Pi3MfQ": true
}
}
With the above structure you can easily read the user_hearts node for the user you're interested in, and then read the poems one by one if needed.
Also see:
Firebase query if child of child contains a value
Firebase Realtime Database - index on location containing uid
So I am wondering about how necessary it is to store variables in the realtime firebase database if I want all Users at access the same dynamic variable.
So for instance, I have a arraylist that stores the list of open games, and if I want this list to update in realtime for every user should this List in firebase realtime database?
Sorry for the simplicity of the question
Yes, it may be a simple question, but it surely pops in head of everyone, once.
I think for updating any list dynamically in real time, would require you to access any kind of database.
It is not necessary to have it on Firebase database, but any database online, that can tell every open instance of your app that the list has to be updated at a particular instant.
The main reason of why you need it to be on database is updating it in real time and that too dynamically.
If it's not dynamic, meaning the content that you need, can be hardcoded then one way would be placing everything you need in your code and using timer or something like that to fire at particular moments to update things in your app.
Also that aside, sorting, storing and changing data is much simpler using a database, which also becomes one more reason for you to use a database like Firebase to keep content of your app that has to be updated frequently in real time.
You can know more about database in this Google link, I found.
I was trying to develop an mobile app which have some similar idea just like Uber, which is real time update driver & customer location. So here I am seeking for suggestion for what I was thinking for the app structure.
For what I research, in order to provide fast real time update location, I may need to make use of real time database such as Firebase for the backend. So, I was thinking to combine 2 different type of database to achieve what I was thinking...
Firebase - For real time fast update user location
MySQL - For backend api business logic
However, I have no experience with firebase, so I hope you all can give some advise. I plan to only store the user location coordinate information in firebase database, then retrieve it from mobile app to update realtime.
My problem is I not sure should I forever persist those driver coordinate data in firebase database? Since the coordinate data keep changing update in firebase, so should I delete those coordinate data from firebase as soon as the driver have reach the destination. (No need to keep those data persist, only real time data keep change on firebase)
Thanks for reading such long question, I will also happy that if you all can remind to me any other concern if I use 2 different database for my application.
You'll typically keep a list of drivers and their locations in Firebase:
driverlocations
driver1id: location
driver2id: location
This means that you're not adding new data, but updating existing data. So you don't have to worry about the list constantly growing.
To ensure you don't have stale data for drivers that closed the app/stopped driving, you can use Firebase's onDisconnect() handlers to remove the data when they disconnect.
Now querying this data for nearby drivers is still tricky. You'll want to look at GeoFire for that. I recently explained why that is needed and how it works here: Sort array by distance near user location from firebase
I have enabled the Firebase Persistance in my application. If I am setting a value to a child such as
child.setValue("XYZ");
I am not adding value to the parent tree. I am just updating the value of one child. So here, the value will be updated again and again by the user as he uses the application like many times a day. So, my question is, if user do not have inter-net connection for days, will this thing generate bug as Firebase is storing these things in cache. Does all the data get stored offline with mechanism something like commits in git or just the latest value is stored. I am asking this thing because it's kind of cache so if firebase stores data with all the logs and values the child gets then it can make my application buggy and slow as it will carry all the cache all the time.
If you are getting offline and you are updating a single record than, when your getting back online, only your last update will be updated on the server. Let's take an example. You have a product in which you store a timestamp. Every time you make an update, you change that timestamp with the current timestamp. If you are offline and you edit that product several times, when you'll be back online, only the last timpstamp will be added on the server.
But remember, this not happening when you add new data. When you do this, all the new data is added on the server accordingly to time you have added. This happening also when you delete.
Hope it helps.
I'm building an android app, and I need to retrieve a list of users from a database. I know how to write the query. I will have back a list of object.
I was wondering how to do this in an efficient way considering that I need that list in 3 activities. I think that repeating the same code for 3 times, in 3 different activities is not optimal.
Thanks
As per you comment you are fetching this user data from server,
you can consider following:
make a web service to retrieve user list.
call the web service first time you need list of users.
cache this list in shared preferences or SQLite DB, depending upon size of list.
use it where ever you need.
refresh your list from server periodically or as per your need.