No need to reformat, just use the script below to put the large primes file in a DBD::SQLite2 database. First, download and unzip the files that contain the first 15 million primes in chunks of 1 million. You will have primes1.txt through primes15.txt in a directory. Run this there:
#!/bin/perl
use strict; use warnings;
use DBI;
my $dbh = DBI>connect('dbi:SQLite2:dbname=primes.db','','',{RaiseErro
+r=>1});
my $cnt = 0;
# 'number' has to be text because of length
$dbh>do('CREATE TABLE primes (id INTEGER, number TEXT)');
for (1..15) { $cnt = add_primes($dbh,$cnt,"primes$_.txt") }
sub add_primes {
my ($db, $c, $filename) = @_;
open my $file, '<', $filename or die("Can't read '$filename': $!")
+;
print STDERR "Adding primes from $filename\n";
#first two lines are not data, skip them
for (1..2) { <$file> }
eval {
$db>begin_work;
my $sth = $db>prepare('INSERT INTO primes (id,number) VALUES
+(?,?)');
while (<$file>) {
foreach ( split(/\s+/,$_) ) { $sth>execute(++$cnt,$_) }
}
$db>commit;
};
if ($@) {
print STDERR "Died while processing prime #$cnt, with error:\n
+$@";
exit;
}
return $cnt;
}
Then you can always ask for the n'th prime with the SQL (? is n)
SELECT number FROM primes WHERE id = ?
