问题
I am making a Moneymanagement-App where the user can create Transfers for each day.
I am currently listing all the data on the mainscreen. At the moment that doesn't matter because there isn't much data but imagine a user who uses the app several years and tracking all his spendings.
My first thought was to cache all the available Data for that user but that would cause too many unnecessary reads because the user most likely won't need the data from lets say 5 years ago.
So I thought the solution would be to just implement pagination for that screen.
But :
The user can get statistics about his spendinghistory on another screen by selecting a category and a timeperiod. Currently i am running a query on those parameters each time they change but this will obviously also lead to a lot of unnecessary reads.
So the problem is, if the user chooses to get statistics from 5 years ago, that Data wouldn't exist in the cache so i would still have to run a query for this time period and then end up with a incomplete cache of that period because i only got some of the Data based on the Query.
Would love to hear your thoughts on this. How would you handle it ?
回答1:
In general: don't run aggregation queries from the client on demand. Instead store aggregated data in the database, and update it as data is written.
So say that you keep some annual totals, such as their balance at the start and end of the year, their total income and spend for that year, probably broken down by categories. That is all information that you could put in a document for each year.
You'd have a structure /users/$uid/totals/$year and you then have the totals in fields in that document. Every time you write a new transaction, you update the totals document for that user for the current year.
If you do this, you'll only need to read the totals document to show totals, and you'll only need to read individual transactions if you want to show individual transactions.
Also see: Is it possible to run aggregation queries in Firestore?
来源：https://stackoverflow.com/questions/60663075/how-to-optimize-firestore-caching-and-querymodeling