Hi monkers,

First post here. I'm using perl professionally for more than a year now but I'm only doing simple tasks. I'm always impressed when I come here because I don't understand half the code I read... and to improve myself I would like to know how you would have done the function posted below.

It's a simple function that I created to do "group by" on rows retrieved by fetchall_arrayref({});

I'm particulary interessed in:

- better style

- performance improvement

- or more black magic ;)

Here my .pl :

#!/usr/bin/perl
use strict;
use Data::Dumper;

my $rows = [    {'Category' => 'Animal',  'Type' => 'Dog', 'Model' => 
+'Labrador',   'Quantity' => 5},
                {'Category' => 'Animal',  'Type' => 'Dog', 'Model' => 
+'Rottweiler', 'Quantity' => 2},
                {'Category' => 'Animal',  'Type' => 'Cat', 'Model' => 
+'Chartreux',  'Quantity' => 4},
                {'Category' => 'Vehicle', 'Type' => 'Car', 'Model' => 
+'Ford',         'Quantity' => 10},
            ];
            
my $groupedRows = rowsGroupBy($rows, ['Category', 'Type'], { 'SUM' => 
+['Quantity'] });

print $groupedRows->{'Animal', 'Dog'}->{'Quantity'};
# 7

print "\n";
print Dumper $groupedRows;
# $VAR1 = {
          # 'AnimalCat' => {
                            # 'Type' => 'Cat',
                            # 'Quantity' => 4,
                            # 'Category' => 'Animal'
                          # },
          # 'VehicleCar' => {
                             # 'Type' => 'Car',
                             # 'Quantity' => 10,
                             # 'Category' => 'Vehicle'
                           # },
          # 'AnimalDog' => {
                            # 'Type' => 'Dog',
                            # 'Quantity' => 7,
                            # 'Category' => 'Animal'
                          # }
        # };

        
# $rows: Array of hash_ref (rows)
# $groupBy: Array of field to use for the group by. Can be empty if yo
+u want to do $options on all rows.
# $options: Hash with following option handled:
#            SUM => @array: Compute the sum.
#            PILE => @array: Create an array containing all values for
+ the field.
#            MAX => @array: The greatest value encountered.
# Return hash_ref with group by as keys (list) if group by is not empt
+y.
# Return hash_ref with $options as keys if group by is empty.
sub rowsGroupBy {
    my($rows, $groupBy, $options) = @_;
    
    return undef if @$rows+0 == 0 || !defined($groupBy);
    
    my $result = {};
    
    foreach my $row (@$rows) {
        my $value;
        my $key = join(chr(28), map { $row->{$_} } @$groupBy);
        
        if(exists($result->{$key})) {
            $value = $result->{$key};
        }
        else {
            $value = {};
            $result->{$key} = $value;
        }
        
        foreach(@$groupBy) {
            $value->{$_} = $row->{$_};
        }
        foreach(@{$options->{'SUM'}}) {
            $value->{$_} += $row->{$_};
        }
        foreach(@{$options->{'PILE'}}) {
            push(@{$value->{$_}}, $row->{$_});
        }
        foreach(@{$options->{'MAX'}}) {
            $value->{$_} = $row->{$_} if !defined($value->{$_}) || $ro
+w->{$_} gt $value->{$_};
        }
        if($options->{'KEEP_UNDERLYING_ROWS'}) {
            push(@{$value->{'UNDERLYING_ROWS'}}, $row);
        }
    }
    return $result->{''} if @$groupBy == 0;
    return $result;
}
[download]

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