The paged "All inboxes" query (MessageDao.pagingUnifiedFolderSummaries:
WHERE folder = ? AND inInbox = 1 ORDER BY timestampMillis DESC) had no
folder-leading index, so it SCANned the whole messages table via
index_messages_timestampMillis and filtered folder/inInbox per row.
Add a (folder, inInbox, timestampMillis) index so the two equality
predicates become an index seek and the ORDER BY is supplied by the
index. EXPLAIN QUERY PLAN for the query goes from
SCAN messages USING INDEX index_messages_timestampMillis
to
SEARCH messages USING INDEX index_messages_folder_inInbox_timestampMillis (folder=? AND inInbox=?)
with no temp B-tree sort.
Pure additive index (no column/table change): bump the Room DB to v20
with MIGRATION_19_20 (CREATE INDEX IF NOT EXISTS), register it in
DatabaseModule, export 20.json, and add a MigrationTest that runs the
migration and asserts the index shape plus the SEARCH plan on real
Android SQLite.
Closes#187
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
JMR-devandClaude Opus 4.8
5a3669f017