Method: (UNDO-OBJECT-COMMIT STANDARD-CACHE T T)

Source

(defmethod undo-object-commit ((cache standard-cache)
                               partial-transaction-id
                               object-id)
  ;; OBJECT-ID is the id of an object that may have been committed by
  ;; PARTIAL-TRANSACTION-ID, but it's also possible that it hasn't
  ;; been committed yet.

  (let ((object-table (object-table cache))
        (heap (heap cache)))

    (when (eql :reserved (object-info object-table object-id))
      ;; It hasn't been committed yet, so we don't need to
      ;; do anything.
      (return-from undo-object-commit nil))

    ;; Walk along the version list, looking for a version
    ;; that was committed by partial-transaction-id.
    (let ((block (object-heap-position object-table object-id))
          (younger nil))
      (loop
       (let ((buffer (load-block heap block :skip-header t)))
         (multiple-value-bind (id nr-slots schema transaction-id older)
             (load-object-fields buffer object-id)
           ;; DO: Don't load id, nr-slots, schema at all!
           (declare (ignore id nr-slots schema)) 
           (cond ((= transaction-id partial-transaction-id)
                  ;; Got it.  Remove from the version list.
                  (if younger
                      (setf (object-version-list younger heap) older)
                    ;; There is no younger version so we're the first
                    ;; in the version list.  If there's an older version,
                    ;; let the object table point to that older version.
                    ;; Otherwise, remove the object table entry.
                    (if older
                        (setf (object-heap-position object-table object-id)
                              older)
                      (delete-object-id object-table object-id)))
                  (return-from undo-object-commit t))
                 ((null older)
                  ;; It hasn't been committed yet, so we don't need to
                  ;; do anything.
                  (return-from undo-object-commit nil))
                 (t
                  ;; Keep trying older versions.
                  (setq younger block
                        block older)))))))))