Speed up retrieval of lemma suggestions #72
Description
Originally reported by: Marcel Bollmann (Bitbucket: mbollmann, GitHub: mbollmann)
Users report that retrieving lemma suggestions can sometimes take up to 7 seconds, which is huge.
The testing script introduced in commit 1e1f888 suggests that the part which retrieves lemma suggestions from other texts within the project (with the same "ascii" token) is a major bottleneck, taking almost a full second for one lookup on the production database.
If there is no evidence for other factors, refactoring this lookup should be considered.
A possible solution could be to introduce another database table which maps (project_id, mod_ascii) pairs to tag_ids of lemma annotations. This table would have to be updated whenever lemma annotations are saved, and could then be used for efficient lookup during retrieval.