}
  }

  /* Assign rails to all rows that are still unassigned.
  ** The first primary child of a row goes on the same rail as
  ** that row.
  */
  inUse = (1<<(p->mxRail+1))-1;
  for(pRow=p->pLast; pRow; pRow=pRow->pPrev){
    int parentRid;
    if( pRow->iRail>=0 ) continue;
    assert( pRow->nParent>0 );
    parentRid = pRow->aParent[0];
    assert( bag_find(&allRids, parentRid) );
    for(pDesc=pRow->pNext; pDesc && pDesc->rid!=parentRid; pDesc=pDesc->pNext){}