$ cat 896650.pl
#!/usr/bin/perl
use strict;
use warnings;

# Generate values
my @cols = ( 0 .. 10 );
my $rows=50000;
my @data = ( [ map { int 100*rand } @cols ] );
my @gen = ( map { [ 100*rand, int 100*(1+$_*$_*$_*rand) ] } @cols );
for my $r (1 .. $rows) {
	for my $c ( @cols ) {
		$data[$r][$c] = int( $data[$r-1][$c]
			+ $gen[$c][0]*rand) % ($gen[$c][1]);
	}
}

# Count distinct column values
my %H;
for (@data) {
	my @v=@$_;
	for my $c (@cols) {
		$H{$c}{$v[$c]}++;
	}
}

# Sort so most diverse comes first
my @colrank = sort { $$b[1] <=> $$a[1] }
              map { [ $_, scalar keys %{$H{$_}} ] } @cols;
my @colOrder = map { $$_[0] } @colrank;

for my $r (@colrank) {
	print "col $$r[0] has $$r[1] values\n";
}
print join(", ", @colOrder), "\n";

print scalar(@data), " rows to process.\n";

my @tmpdata = @data;
my @keycols = ( shift @colOrder );
while (keys %H < @tmpdata) {
	print scalar(@tmpdata), " rows to process.\n";
	%H=();
	for (@tmpdata) {
		my $key=join(".", @$_[@keycols]);
		$H{$key}++;
	}
	print "cols(", join(",",@keycols), ") give ",
	      scalar(keys %H), " rows.\n";
	push @keycols, shift @colOrder;
}

$ perl 896650.pl
col 10 has 37754 values
col 9 has 29806 values
col 8 has 29772 values
col 7 has 22835 values
col 6 has 16081 values
col 5 has 10136 values
col 3 has 2726 values
col 4 has 559 values
col 2 has 216 values
col 1 has 176 values
col 0 has 1 values
10, 9, 8, 7, 6, 5, 3, 4, 2, 1, 0
50001 rows to process.
50001 rows to process.
cols(10) give 37754 rows.
50001 rows to process.
cols(10,9) give 49996 rows.
50001 rows to process.
cols(10,9,8) give 50001 rows.