The approach will definitely help with optimizing individual queries.
The other level I'd like to know about is if content is indeed indexed when I think it should be and which indexing approach is best. We have batch processes in multiple layers and I'm not sure that our approach to them is optimal when calling processes from a web interface. Example:
1. (For each //element without @id, add @id) then db:optimise and redirect to next step 2. For each /*, process content to XLIFF (uses the new ids so requires preceding redirect to commit changes).
Now, is it suggested to work with updindex/autooptimize to true or as shown above... call optimize manually on step1. Does is even make a difference?