Deleting a category can be very long
When you have many transactions with a given category, deleting this category (with or without replacing it) is very long. This is due to the fact we modify each transaction 1 by 1, and not batch editing the transactions in a single SQL transaction. For example, on 1 year of transactions, if a I modify 10-20% of the transactions, it takes more than 2 seconds. I have tried a similar situation with a single transaction, it takes 50ms (with SQLite).