Re: Eliminate exact duplicates from array of hashes

It does work, it's just that you don't understand what it's comparing and why they look different to uniq. Each element in your @test_data is a separate hashref which will compare differently with another hashref which might have identical contents.

For this particular usage with this (relatively small) amount of data you might could kludge something up by serializing items and then checking the serialized version.

Update: Ooops, forgot to enable sorting of keys with canonical(1). Updated output as well. I did say it was a kludge . . .

use 5.018;
use Data::Dumper;
use JSON::XS;

my @test_data = (
    { Tag1 => "1", Tag2 => "a" },
    { Tag1 => "1", Tag2 => "a" },
    { Tag1 => "1", Tag2 => "b" },
    { Tag1 => "1", Tag2 => "c" },
    { Tag1 => "1", Tag2 => "a" },
    { Tag1 => "2", Tag2 => "a" },
    { Tag1 => "2", Tag2 => "d" },
    { Tag1 => "2", Tag2 => "a" },
    { Tag1 => "3"},
    { Tag1 => "sun", Tag2 => "a" },
    { Tag1 => "sun", Tag2 => "a" },
);

## showing the hashrefs are different regardless of contents
say qq{idx: $_\tref: $test_data[$_]} for 0..2;

my $j = JSON::XS->new->pretty(0)->ascii(1)->canonical(1);

my %seen_items;
my @unique;
for my $item ( @test_data ) {
  my $ser = $j->encode( $item );
  push @unique, $item unless $seen_items{ $ser }++;
}

print Dumper \@unique;
__END__
idx: 0    ref: HASH(0x7fb3ac003ee8)
idx: 1    ref: HASH(0x7fb3ac015cf8)
idx: 2    ref: HASH(0x7fb3ac015dd0)
$VAR1 = [
          {
            'Tag1' => '1',
            'Tag2' => 'a'
          },
          {
            'Tag2' => 'b',
            'Tag1' => '1'
          },
          {
            'Tag1' => '1',
            'Tag2' => 'c'
          },
          {
            'Tag1' => '2',
            'Tag2' => 'a'
          },
          {
            'Tag1' => '2',
            'Tag2' => 'd'
          },
          {
            'Tag1' => '3'
          },
          {
            'Tag1' => 'sun',
            'Tag2' => 'a'
          }
        ];
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Comment on Re: Eliminate exact duplicates from array of hashes Select or Download Code

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Re^2: Eliminate exact duplicates from array of hashes by Anonymous Monk on Oct 09, 2019 at 18:03 UTC
Interesting approach, thank you. However, it does not seem to work. It eliminates only 1 duplicate, while there are much more exact duplicates in my array (I guess it has to do with the order of the couples key/values inside the hash).	[reply]