in reply to Merge hashes in specific format

#!/usr/bin/perl

# https://perlmonks.org/?node_id=1228412

use strict;
use warnings;

my $one =
  {
  data  => {
             dir1 => {
                       fileA => { pid => { 61781 => 1 }, total => 13 }
+,
                       fileB => { pid => { 61799 => 1 }, total => 12 }
+,
                     },
             dir2 => {
                       fileA => { pid => { 61439 => 1 }, total => 5 },
                       fileC => { pid => { 12345 => 1 }, total => 10 }
+,
                     },
           },
  total => { fileA => 18, fileB => 12, fileC => 10 },
  };

my $two =
  {
  data  => {
             dir3 => {
                       fileA => { pid => { 616161 => 1 }, total => 6 }
+,
                       fileD => { pid => { 54321 => 1 }, total => 12 }
+,
                     },
             dir4 => {
                       fileA => { pid => { 1718 => 1 }, total => 2 },
                       fileE => { pid => { 15151 => 1 }, total => 3 },
                     },
           },
  total => { fileA => 8, fileD => 12, fileE => 3 },
  };

my $newhash = 
  {
  data => { %{ $one->{data} }, %{ $two->{data} } },
  total => do
    {
    my %total;
    for my $href ( $one, $two )
      {
      $total{$_} += $href->{total}{$_} for keys %{ $href->{total} };
      }
    \%total;
    }
  };

use Data::Dump 'dd'; dd $newhash;

[download]

Outputs: 

{
  data  => {
             dir1 => {
                       fileA => { pid => { 61781 => 1 }, total => 13 }
+,
                       fileB => { pid => { 61799 => 1 }, total => 12 }
+,
                     },
             dir2 => {
                       fileA => { pid => { 61439 => 1 }, total => 5 },
                       fileC => { pid => { 12345 => 1 }, total => 10 }
+,
                     },
             dir3 => {
                       fileA => { pid => { 616161 => 1 }, total => 6 }
+,
                       fileD => { pid => { 54321 => 1 }, total => 12 }
+,
                     },
             dir4 => {
                       fileA => { pid => { 1718 => 1 }, total => 2 },
                       fileE => { pid => { 15151 => 1 }, total => 3 },
                     },
           },
  total => { fileA => 26, fileB => 12, fileC => 10, fileD => 12, fileE
+ => 3 },
}

[download]

Replies are listed 'Best First'.
Re^2: Merge hashes in specific format
by Veltro (Hermit) on Jan 13, 2019 at 18:50 UTC

    Hi tybalt89,

    Sorry to post this so late but I couldn't find time to do this earlier. I have a question regards your technique to merge and the one that I posted.

    With the method that I posted I specifically did not choose to use Hash::Merge and also specifically not { ( %{ $ ... }, %{ $ ... } ) } but instead to make it LEFT_PRECEDENT on the dir1 .. dirN. (Even though the design criteria said that these elements would be unique). The method that I created would ignore any new 'dir' element that already existed and so it will not corrupt already collected data.

    If I would have used Hash::Merge I would have probably done something like:

    use strict ;
use warnings ;
use Data::Dumper ;
use List::Util qw { sum0 } ;
use Hash::Merge ;

my $VAR1 = {
     # Same as before
        };
my $VAR2 = {
    # same as before
        };
my $merger = Hash::Merge->new('RETAINMENT_PRECEDENT');
my $VAR3 = $merger->merge( $VAR1, $VAR2 ) ;
foreach(keys %{$VAR3->{ total }}) {
    if ( ref $VAR3->{ total }->{ $_ } eq 'ARRAY' ) {
        $VAR3->{ total }->{ $_ } = sum0 @{$VAR3->{ total }->{ $_ }} ;
    }
}
print Dumper( $VAR3 ) ;

    [download]

    When receiving 'dir' elements again and using the technique of { ( %{ $ ... }, %{ $ ... } ) } would corrupt the data:

    • different pid: data loss
    • calculates wrong totals

    My question basically is, which of the three techniques is in your opinion more robust. Even though I directed this question to tybalt89, anyone else feel free to answer as well of course.

[reply]
[d/l]
[select]

      "the design criteria said that these elements would be unique"

      If the specification changes, then I can charge extra to adapt it :)

[reply]
Re^2: Merge hashes in specific format
by ovedpo15 (Pilgrim) on Jan 12, 2019 at 21:53 UTC
    Great, thank you. How to make $newhash to be a real hash? Isn't it a scalar right now?
[reply]

      It is a scalar anonymous hash reference. If by "real hash" you mean "not an anonymous hash reference", try (untested):
          my %newhash = ( data => { ... }, total => do { ... }, );

      Give a man a fish:  <%-{-{-{-<

[reply]
[d/l]
[select]
        So I have done the following sub:
            foreach my $dir (@{$dirs})
    {
        decode($dir.".data.json",%data); # will change name
        my $final_href = 
        {
            data => { ( %{$final_href->{data} },%{ $data{data} } ) },
            total => do
            {
                my %total;
                for my $href ( $final_href->{total}, $data{total} ) {
                    $total{$_} += $href->{total}{$_} for keys %{ $href
+->{total} };
                }
            \%total;
            }
        };

        [download]
        But it will fail because at start $final_href->{data} is not defined. How to make it work even if its not defined (in that case I should just get the $data{$data}
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom