It looks like it only partially reindexes on save, but it completely reindexes the single file that’s saved, rather than doing partial reindex of the file on every keystroke like rust-analyser.
But importantly it’s not reindexing the entire project, which is the expensive operation. So you have higher peak RAM when opening a brand new project, but much lower RAM usage while working on the project.
But importantly it’s not reindexing the entire project, which is the expensive operation. So you have higher peak RAM when opening a brand new project, but much lower RAM usage while working on the project.