view release on metacpan or  search on metacpan

src/subversion/subversion/libsvn_fs_base/tree.c  view on Meta::CPAN

  svn_revnum_t youngest_rev;
  const svn_fs_id_t *y_rev_root_id;
  dag_node_t *txn_base_root_node;

  /* Getting the youngest revision locks the revisions table until
     this trail is done. */
  SVN_ERR(svn_fs_bdb__youngest_rev(&youngest_rev, fs, trail, trail->pool));

  /* If the root of the youngest revision is the same as txn's base,
     then no further merging is necessary and we can commit. */
  SVN_ERR(svn_fs_base__rev_get_root(&y_rev_root_id, fs, youngest_rev,
                                    trail, trail->pool));
  SVN_ERR(svn_fs_base__dag_txn_base_root(&txn_base_root_node, fs, txn_name,
                                         trail, trail->pool));
  /* ### kff todo: it seems weird to grab the ID for one, and the node
     for the other.  We can certainly do the comparison we need, but
     it would be nice to grab the same type of information from the
     start, instead of having to transform one of them. */
  if (! svn_fs_base__id_eq(y_rev_root_id,
                           svn_fs_base__dag_get_id(txn_base_root_node)))
    {
      svn_string_t *id_str = svn_fs_base__id_unparse(y_rev_root_id,
                                                     trail->pool);
      return svn_error_createf
        (SVN_ERR_FS_TXN_OUT_OF_DATE, NULL,
         _("Transaction '%s' out-of-date with respect to revision '%s'"),
         txn_name, id_str->data);
    }

  /* Locks may have been added (or stolen) between the calling of
     previous svn_fs.h functions and svn_fs_commit_txn(), so we need
     to re-examine every changed-path in the txn and re-verify all
     discovered locks. */
  SVN_ERR(verify_locks(txn_name, trail, trail->pool));

  /* Else, commit the txn. */
  return svn_fs_base__dag_commit_txn(&(args->new_rev), txn, trail,
                                     trail->pool);
}


/* Note:  it is acceptable for this function to call back into
   top-level FS interfaces because it does not itself use trails.  */
svn_error_t *
svn_fs_base__commit_txn(const char **conflict_p,
                        svn_revnum_t *new_rev,
                        svn_fs_txn_t *txn,
                        apr_pool_t *pool)
{
  /* How do commits work in Subversion?
   *
   * When you're ready to commit, here's what you have:
   *
   *    1. A transaction, with a mutable tree hanging off it.
   *    2. A base revision, against which TXN_TREE was made.
   *    3. A latest revision, which may be newer than the base rev.
   *
   * The problem is that if latest != base, then one can't simply
   * attach the txn root as the root of the new revision, because that
   * would lose all the changes between base and latest.  It is also
   * not acceptable to insist that base == latest; in a busy
   * repository, commits happen too fast to insist that everyone keep
   * their entire tree up-to-date at all times.  Non-overlapping
   * changes should not interfere with each other.
   *
   * The solution is to merge the changes between base and latest into
   * the txn tree [see the function merge()].  The txn tree is the
   * only one of the three trees that is mutable, so it has to be the
   * one to adjust.
   *
   * You might have to adjust it more than once, if a new latest
   * revision gets committed while you were merging in the previous
   * one.  For example:
   *
   *    1. Jane starts txn T, based at revision 6.
   *    2. Someone commits (or already committed) revision 7.
   *    3. Jane's starts merging the changes between 6 and 7 into T.
   *    4. Meanwhile, someone commits revision 8.
   *    5. Jane finishes the 6-->7 merge.  T could now be committed
   *       against a latest revision of 7, if only that were still the
   *       latest.  Unfortunately, 8 is now the latest, so...
   *    6. Jane starts merging the changes between 7 and 8 into T.
   *    7. Meanwhile, no one commits any new revisions.  Whew.
   *    8. Jane commits T, creating revision 9, whose tree is exactly
   *       T's tree, except immutable now.
   *
   * Lather, rinse, repeat.
   */

  svn_error_t *err;
  svn_fs_t *fs = txn->fs;
  apr_pool_t *subpool = svn_pool_create(pool);

  /* Initialize output params. */
  *new_rev = SVN_INVALID_REVNUM;
  if (conflict_p)
    *conflict_p = NULL;

  while (1729)
    {
      struct get_root_args get_root_args;
      struct merge_args merge_args;
      struct commit_args commit_args;
      svn_revnum_t youngish_rev;
      svn_fs_root_t *youngish_root;
      dag_node_t *youngish_root_node;

      svn_pool_clear(subpool);

      /* Get the *current* youngest revision, in one short-lived
         Berkeley transaction.  (We don't want the revisions table
         locked while we do the main merge.)  We call it "youngish"
         because new revisions might get committed after we've
         obtained it. */

      SVN_ERR(svn_fs_base__youngest_rev(&youngish_rev, fs, subpool));
      SVN_ERR(svn_fs_base__revision_root(&youngish_root, fs, youngish_rev,
                                         subpool));

      /* Get the dag node for the youngest revision, also in one
         Berkeley transaction.  Later we'll use it as the SOURCE