Marshall, that's a good point regarding db-operations. You are right that there is memory cost for the performance boost of using refs with this specific use-case: db-IO. I was talking more generally so probably I gave the wrong impression for this specific case. Anyway refreshing on the manual is good.

According to fetchall_arrayref of DBI a tradeoff would be to fetchall_arrayref() in batches but still use array-refs, as

That might be the fastest way to fetch and process lots of rows using the DBI, but it depends on the relative cost of method calls vs memory allocation.

my $rows = []; # cache for batches of rows
while( my $row = ( shift(@$rows) || # get row from cache, or reload ca
+che:
                   shift(@{$rows=$sth->fetchall_arrayref(undef,10_000)
+||[]}) )
) {
  ...
}
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bw, bliako