The startup seq repair (runMigrations) assigned seq to NULL-seq sessions
one UPDATE per point. Merge/split leave seq=NULL by design, so recent
merged tracks (10865 + 3614 points) meant ~15000 sequential IPC writes on
every launch - and for the big sessions the writes did not persist before
the next launch re-ran the whole thing. That was the slow start.
Replace it with the batched CASE re-sequence (chunks of 300, like
saveGapFill/saveSmoothedTrack): ~50 UPDATEs instead of ~15000. Verified on
device: repair of all 3 sessions dropped from ~15s to ~1.1s, seq now
persists so it is one-time (boot 2 does no repair, migrations 357ms), 0
NULL seq left, seq matches ts order (0 inversions).
4aiman
74f3ec4d6e