I have created an archive table which will store data for selecting only.

Daily there will be a program to transfer a batch of records into the archive table. There are several columns which are indexed; while others are not.

I am concerned with time cost per batch insertion:
- 1st batch insertion: N1
- 2nd batch insertion: N2
- 3rd batch insertion: N3

The question is: will N1, N2, and N3 roughly be the same, or N3 > N2 > N1?

That is, will the time cost be a constant or incremental, with existence of several indexes?

All indexes are non-clustered.

The archive table structure is this:

create table document (
   doc_id   int unsigned primary key,
   owner_id int,  -- indexed
   title    smalltext,
   country  char(2),
   year     year(4),
   time     datetime,

   key ix_owner(owner_id)
}