message: push_str is fastest, also with_capacity
diff: @@ -10,12 +10,17 @@ pub fn wql_to_sql<'a>(class: &'a Vec<u8>, op: &'a Operator, _options: Option<&st
  let mut arguments: Vec<&ToSql> = Vec::new();
  arguments.push(class);
  let clause_string = operator_to_sql(op, &mut arguments)?;
  - let mut query_string = "SELECT i.id, i.name, i.value, i.key, i.type FROM items as i WHERE i.type = ?".to_string();
  + const BASE: &str = "SELECT i.id, i.name, i.value, i.key, i.type FROM items as i WHERE i.type = ?";
  if !clause_string.is_empty() {
  + let mut query_string = String::with_capacity(BASE.len() + 5 + clause_string.len());
  + query_string.push_str(BASE);
  query_string.push_str(" AND ");
  query_string.push_str(&clause_string);
  - }
  Ok((query_string, arguments))
  + } else {
  + Ok((BASE.to_string(), arguments))
  + }
  +
  }
  