Deluan 1c83f36ddf perf(persistence): make album list pages index-served
The two album list requests reported in discussion #5929 (a 110k-album,
two-library instance) were dominated by work that scaled with the whole
library instead of the page:

- Every native API list request also runs a count for the X-Total-Count
  header. album had no index covering library_id, so that count scanned the
  entire table on every request, dragging each row's JSON blobs through the
  page cache. count(distinct id) additionally built a temp b-tree over the
  full result set even when the query had no join that could duplicate rows.
- A random sort cannot be served by an index, so SQLite evaluated SEEDEDRAND
  for every matching row and pushed each one, with its library and annotation
  joins and full column projection, through a sorter that kept only 36 rows.

Add an album(id, library_id) index so library-filtered counts are served by a
covering index scan, and make the shared count() helper use count(*) when the
rendered query has no join, keeping count(distinct id) wherever a join could
fan out rows. id leads the index deliberately: with library_id leading, the
planner drives sorted list queries off it and sorts an entire library rather
than walking a sort-satisfying index, and fresh statistics do not change that
choice.

Resolve random pages by id before hydrating them, so the sort pass runs on
that covering index with no joins and only the page itself is materialized.
Pages larger than 1000 keep the single-query path. The seeded shuffle is
unchanged: the id query carries the caller's options, so SEEDEDRAND, explicit
seeds, and the reseed-only-at-offset-0 rule all still apply, and the page is
reordered in Go to preserve it.

Also make the album name sort a total order by appending album.id, and widen
album_order_album_name to (order_album_name, order_album_artist_name, id) to
serve it. Without a tiebreaker, equal names made page order plan-dependent,
which can skip or duplicate rows across paginated requests.
2026-08-10 15:41:22 -04:00
..