(define (dg-debug-display-content-left->right txn) (status-t dg-txn-t*)
  status-init
  (dg-mdb-introduce-cursor txn left->right)
  (define
    id-left dg-id-t
    id-right dg-id-t
    id-label dg-id-t
    ordinal dg-ordinal-t)
  dg-mdb-introduce-val-relation-key
  dg-mdb-introduce-val-relation-data
  (printf "left->right\n")
  (dg-mdb-cursor-each-key
    left->right
    val-relation-key
    val-relation-data
    (compound-statement
      (set
        id-left (dg-mdb-val->id-at val-relation-key 0)
        id-label (dg-mdb-val->id-at val-relation-key 1))
      (do-while dg-mdb-status-success?
        (set
          id-right (dg-mdb-val-relation-data->id val-relation-data)
          ordinal (dg-mdb-val-relation-data->ordinal val-relation-data))
        (printf "  (%lu %lu) (%lu %lu)\n" id-left id-label ordinal id-right)
        (dg-mdb-cursor-next-dup! left->right val-relation-key val-relation-data))))
  (label exit
    (mdb-cursor-close left->right)
    dg-status-success-if-mdb-notfound
    (return status)))

(define (dg-debug-display-content-right->left txn) (status-t dg-txn-t*)
  status-init
  (dg-mdb-introduce-cursor txn right->left)
  (define
    id-left dg-id-t
    id-right dg-id-t
    id-label dg-id-t)
  dg-mdb-introduce-val-relation-key
  dg-mdb-introduce-val-id
  (printf "right->left\n")
  (dg-mdb-cursor-each-key
    right->left
    val-relation-key
    val-id
    (compound-statement
      (set
        id-right (dg-mdb-val->id-at val-relation-key 0)
        id-label (dg-mdb-val->id-at val-relation-key 1))
      (do-while dg-mdb-status-success?
        (set id-left (dg-mdb-val->id val-id))
        (printf "  (%lu %lu) %lu\n" id-right id-label id-left)
        (dg-mdb-cursor-next-dup! right->left val-relation-key val-id))))
  (label exit
    (mdb-cursor-close right->left)
    dg-status-success-if-mdb-notfound
    (return status)))