(pre-define (dg-relation-data-ordinal-set relation-data value)
  (array-set-index (convert-type relation-data dg-ordinal-t*) 0 value))

(pre-define (dg-relation-data-id-set relation-data value)
  (array-set-index (convert-type (+ 1 (convert-type relation-data dg-ordinal-t*)) dg-id-t*) 0 value))

(pre-define (dg-define-relation-key name) (define-array name dg-id-t (2) 0 0))

(pre-define (dg-define-relation-data name)
  (define-array name b8 ((+ dg-size-octets-ordinal dg-size-octets-id)))
  (memset name 0 (+ dg-size-octets-ordinal dg-size-octets-id)))

(pre-define (dg-define-relation-record name)
  (define name dg-relation-record-t (struct-literal 0 0 0 0)))

(pre-define (dg-relation-records-add! target record target-temp)
  (dg-pointer-allocation-set target (dg-relation-records-add target record) target-temp))

(define (dg-mdb-left->right-seek-right left->right id-right) (status-t MDB-cursor* dg-id-t)
  "search data until the given id-right has been found" status-init
  dg-mdb-introduce-val-relation-key dg-mdb-introduce-val-relation-data
  (dg-mdb-cursor-get! left->right val-relation-key val-relation-data MDB-GET-CURRENT)
  (label each-data
    (if dg-mdb-status-success?
      (if (= id-right (dg-mdb-val-relation-data->id val-relation-data)) (return status)
        (begin (dg-mdb-cursor-next-dup! left->right val-relation-key val-relation-data)
          (goto each-data)))
      dg-mdb-status-require-notfound))
  (label exit (return status)))

(define (dg-relation-ensure txn left right label ordinal-generator ordinal-generator-state)
  (status-t dg-txn-t* dg-ids-t* dg-ids-t* dg-ids-t* dg-relation-ordinal-generator-t b0*) status-init
  (define right-pointer dg-ids-t*
    label-pointer dg-ids-t* id-left dg-id-t id-right dg-id-t id-label dg-id-t)
  (define ordinal dg-ordinal-t
    (if* (and (not ordinal-generator) ordinal-generator-state)
      (set ordinal (deref (convert-type ordinal-generator-state dg-ordinal-t*))) 0))
  (dg-define-relation-key relation-key) (dg-define-relation-data relation-data)
  dg-mdb-introduce-val-id dg-mdb-introduce-val-id-2
  dg-mdb-introduce-val-relation-key dg-mdb-introduce-val-relation-data
  (dg-mdb-introduce-cursor-3 txn left->right right->left label->left)
  (while left (set id-left (dg-ids-first left) label-pointer label)
    (while label-pointer (set id-label (dg-ids-first label-pointer) right-pointer right)
      (struct-set val-id-2 mv-data (address-of id-label))
      (while right-pointer (set id-right (dg-ids-first right-pointer))
        (array-set-index relation-key 0 id-right 1 id-label)
        (struct-set val-relation-key mv-data relation-key)
        (struct-set val-id mv-data (address-of id-left))
        (dg-mdb-cursor-get! right->left val-relation-key val-id MDB-GET-BOTH)
        (if (= MDB-NOTFOUND status.id)
          (begin
            (dg-mdb-status-require!
              (mdb-cursor-put right->left (address-of val-relation-key) (address-of val-id) 0))
            (dg-mdb-status-require!
              (mdb-cursor-put label->left (address-of val-id-2) (address-of val-id) 0))
            (array-set-index relation-key 0 id-left 1 id-label)
            (if ordinal-generator (set ordinal ((deref ordinal-generator) ordinal-generator-state)))
            (dg-relation-data-ordinal-set relation-data ordinal)
            (dg-relation-data-id-set relation-data id-right)
            (struct-set val-relation-data mv-data relation-data)
            (dg-mdb-status-require!
              (mdb-cursor-put left->right (address-of val-relation-key)
                (address-of val-relation-data) 0)))
          (if (not dg-mdb-status-success?) (status-set-group-goto dg-status-group-lmdb)))
        (set right-pointer (dg-ids-rest right-pointer)))
      (set label-pointer (dg-ids-rest label-pointer)))
    (set left (dg-ids-rest left)))
  (label exit (dg-mdb-cursor-close-3 left->right right->left label->left) (return status)))

(sc-include-once sph-dg-relation-delete "relation-delete"
  sph-dg-relation-read "relation-read" sph-dg-debug-relation "lib/debug-relation")