Support for Transactions

[samedhi]

Firebase (Firestore) has the ability to do transactional writes. Transactions are often necessary to correctly write data. Firebase transactions on the web seem to be in the form of writing a js function that reads 0 or more entities, and then writes 0 or more entities. Can we get this working on firemore within cljs as well?

https://firebase.google.com/docs/firestore/manage-data/transactions

[samedhi]

My curent thinking is to write a macro of this form

(transaction!
  [symbol1 <ref1> 
   symbol2 <ref2> 
   symbolN <refN>] ;; documents to read
  (write! ...)
  (merge! ...)
  (delete! ...))

Where the return value is the return (or error) of the transaction.

What if I need to read a document, then based on something in the document, read another document. Could it look like this?

(transaction!
  [symbol1 <ref1>]
  (transaction!
   [symbol2 (:id-to-read symbol1)]
    (write! (:id symbol2) (cross-document-fx symbol1 symbol2))))

OR

(transaction!
  [symbol1 <ref1>
   symbol2 (:id-to-read symbol1)]
  (write! (:id symbol2) (cross-document-fx symbol1 symbol2)))

I think the later is better, but it implies that the reads are being done sequentially.