sqlite: add migration index

persist/sqlite/init.sql

@@ -58,6 +58,7 @@ CREATE TABLE volume_sectors (
 	UNIQUE (volume_id, volume_index)
 );
 CREATE INDEX volume_sectors_volume_id_sector_id_volume_index_compound ON volume_sectors(volume_id, sector_id, volume_index) WHERE sector_id IS NULL;
+CREATE INDEX volume_sectors_volume_id_sector_id_volume_index_set_compound ON volume_sectors (volume_id, sector_id, volume_index) WHERE sector_id IS NOT NULL;
 CREATE INDEX volume_sectors_volume_id_sector_id ON volume_sectors(volume_id, sector_id);
 CREATE INDEX volume_sectors_volume_id ON volume_sectors(volume_id);
 CREATE INDEX volume_sectors_volume_index ON volume_sectors(volume_index ASC);

persist/sqlite/migrations.go

@@ -9,6 +9,12 @@ import (
 	"go.sia.tech/hostd/host/contracts"
 )
 
+// migrateVersion20 adds a compound index to the volume_sectors table
+func migrateVersion20(tx txn) error {
+	_, err := tx.Exec(`CREATE INDEX volume_sectors_volume_id_sector_id_volume_index_set_compound ON volume_sectors (volume_id, sector_id, volume_index) WHERE sector_id IS NOT NULL;`)
+	return err
+}
+
 // migrateVersion19 adds a compound index to the volume_sectors table
 func migrateVersion19(tx txn) error {
 	const query = `
@@ -505,4 +511,5 @@ var migrations = []func(tx txn) error{
 	migrateVersion17,
 	migrateVersion18,
 	migrateVersion19,
+	migrateVersion20,
 }

persist/sqlite/volumes.go

@@ -521,7 +521,8 @@ func sectorForMigration(tx txn, volumeID int64, minIndex uint64) (loc storage.Se
 	const query = `SELECT vs.id, vs.volume_id, vs.volume_index, s.sector_root
 	FROM volume_sectors vs
 	INNER JOIN stored_sectors s ON (s.id=vs.sector_id)
-	WHERE vs.sector_id IS NOT NULL AND vs.volume_id=$1 AND vs.volume_index >= $2`
+	WHERE vs.sector_id IS NOT NULL AND vs.volume_id=$1 AND vs.volume_index >= $2
+	LIMIT 1`
 
 	err = tx.QueryRow(query, volumeID, minIndex).Scan(&loc.ID, &loc.Volume, &loc.Index, (*sqlHash256)(&loc.Root))
 	if errors.Is(err, sql.ErrNoRows) {