I see that you're using fetchrow_hashref, so I will point out the following caveat from the DBI documentation:

  fetchrow_hashref

    ...

    Because of the extra work fetchrow_hashref and Perl
    have to perform, it is not as efficient as
    fetchrow_arrayref or fetchrow_array.
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Of course, if you switch to fetchrow_array or fetchrow_arrayref, you will have to be careful about the order of the column names in the SELECT statement, but I think it's worth it if you want to improve efficiency.