The foreign key index check took every index from PRAGMA index_list as a
usable prefix, partial ones included. An index like
CREATE INDEX ix ON c(p_id) WHERE state = 'open' would satisfy FKIDX-001,
yet the cascade lookup WHERE p_id = ? still scans the table, which is the
regression the check exists to catch. A partial index now counts only when
its predicate is IS NOT NULL on the key's own columns, the one form SQLite
can prove from p_id = ?. Nothing in today's schema depends on a partial
index alone, so the result on the migrated snapshot is unchanged.
Maurice
a198dde5d2