So one of my favorite features of Looker is the persistent derived tables and the data modeling functionality that comes with that - it allows us to be very nimble. However, one of the downsides of using persistent derived tables is that every time it gets generated, unless you are setting a filter for it constrain the time period, the time it takes to generate takes longer and longer as your data set grows.
However, a lot of the times really only a small portion of the PDT needs to be updated (think a user_order_facts table or something like that).
My question is, is there a way to only re-compute the parts of the derived table which have changed since the last time it was built? Or should I be looking more towards an ETL solution at this point?