解析大(100 Mb)
XML文件时出现“Out of memory”错误
use strict;
use warnings;
use XML::Twig;
my $twig=XML::Twig->new();
my $data = XML::Twig->new
->parsefile("divisionhouserooms-v3.xml")
->simplify( keyattr => []);
my @good_division_numbers = qw( 30 31 32 35 38 );
foreach my $property ( @{ $data->{DivisionHouseRoom}}) {
my $house_code = $property->{HouseCode};
print $house_code,"\n";
my $amount_of_bedrooms = 0;
foreach my $division ( @{ $property->{Divisions}->{Division} } ) {
next unless grep { $_ eq $division->{DivisionNumber} } @good_division_numbers;
$amount_of_bedrooms += $division->{DivisionQuantity};
}
open my $fh,">>","Result.csv" or die $!;
print $fh join("\t",$house_code,$amount_of_bedrooms),"\n";
close $fh;
}
解决方法
处理不适合内存的大型XML文件是
XML::Twig
advertises：
One of the strengths of
XML::Twigis that it let you work with files
that do not fit in memory (BTW storing an XML document in memory as a
tree is quite memory-expensive,the expansion factor being often
around 10).To do this you can define handlers,that will be called once a
specific element has been completely parsed. In these handlers you can
access the element and process it as you see fit (…)
问题中发布的代码根本没有充分利用XML :: Twig的优势(使用简化方法并没有比XML::Simple更好).
代码中缺少的是’twig_handlers’或’twig_roots’,这实际上导致解析器有效地关注XML文档内存的相关部分.
很难说没有看到XML是processing the document chunk-by-chunk还是just selected parts,但任何一个都应该解决这个问题.
所以代码应该类似于以下内容(chunk-by-chunk演示)：
use strict;
use warnings;
use XML::Twig;
use List::Util 'sum'; # To make life easier
use Data::Dump 'dump'; # To see what's going on
my %bedrooms; # Data structure to store the wanted info
my $xml = XML::Twig->new (
twig_roots => {
DivisionHouseRoom => \&count_bedrooms,}
);
$xml->parsefile( 'divisionhouserooms-v3.xml');
sub count_bedrooms {
my ( $twig,$element ) = @_;
my @divParents = $element->children( 'Divisions' );
my $id = $element->first_child_text( 'HouseCode' );
for my $divParent ( @divParents ) {
my @divisions = $divParent->children( 'Division' );
my $total = sum map { $_->text } @divisions;
$bedrooms{$id} = $total;
}
$element->purge; # Free up memory
}
dump \%bedrooms;