"How many images still owe a quality reading" was a correlated EXISTS per
image over `faces`, and the face row is 8 KB of embedding and crop before
the column it looks at, so each count opened every row. Six such counts
run on every open of the Identity screen and at the end of every sweep:
160 ms on the reference library.
V19 adds three partial indexes holding only the faces still owing each
pass, keyed on the image and carrying the model id the predicate reads,
and replaces `faces_image` with `(image_id, model_id)` so "does this image
hold this embedder's faces" is answered from the index too. The planner
takes a partial index when the count is driven from `faces` and ignores it
inside the EXISTS, so `Needs::Face` carries the per-face fragment and
`repairs::count` spells the query from the faces' side; the list and the
per-image check keep the EXISTS. A test holds the two spellings to the
same answer for every repair.
dtourolle
388bda6af3