static void checkActiveVdbeCnt(sqlite3 *db){
  Vdbe *p;
  int cnt = 0;
  int nWrite = 0;
  int nRead = 0;
  p = db->pVdbe;
  while( p ){
    if( sqlite3_stmt_busy((sqlite3_stmt*)p) ){
      cnt++;
      if( p->readOnly==0 ) nWrite++;
      if( p->bIsReader ) nRead++;
    }
    p = p->pNext;
  }
  assert( cnt==db->nVdbeActive );
  assert( nWrite==db->nVdbeWrite );
  assert( nRead==db->nVdbeRead );
}