/** * INTERNAL: Returns the first field from each of the owned tables, used for fine-grained * pessimistic locking. */ protected Vector getForUpdateOfFields() { Vector allFields = getFields(); int expected = getTableAliases().size(); Vector firstFields = new Vector(expected); DatabaseTable lastTable = null; DatabaseField field = null; int i = 0; // The following loop takes O(n*m) time. n=# of fields. m=#tables. // However, in the m=1 case this will take one pass only. // Also assuming that fields are generally sorted by table, this will // take O(n) time. // An even faster way may be to go getDescriptor().getAdditionalPrimaryKeyFields. while ((i < allFields.size()) && (firstFields.size() < expected)) { field = (DatabaseField) allFields.elementAt(i++); if ((lastTable == null) || !field.getTable().equals(lastTable)) { lastTable = field.getTable(); int j = 0; while (j < firstFields.size()) { if (lastTable.equals(((DatabaseField) firstFields.elementAt(j)).getTable())) { break; } j++; } if (j == firstFields.size()) { firstFields.addElement(field); } } } return firstFields; }