What's That Noise?! [Ian Kallen's Weblog]

« Technorati Cosmos... | Main | Open Source Language... »

20060105 Thursday January 05, 2006

Regexp'ing simple XML

I ran a test to prove to myself that for simple XML documents, the best way to parse them may be to skip capital P parsing altogether and just use a plain-old regular expression pattern match.

The XML format I wanted to test is the response from the Technorati /bloginfo API. I threw together a Perl based benchmark quickly enough and here are the results:

Benchmark: timing 10000 iterations of regexp, xpath...
    regexp:  0 wallclock secs ( 0.13 usr +  0.00 sys =  0.13 CPU) @ 76923.08/s (n=10000)
            (warning: too few iterations for a reliable count)
     xpath: 137 wallclock secs (136.17 usr +  0.04 sys = 136.21 CPU) @ 73.42/s (n=10000) 
... the regexp parse was three orders of magnitude faster than the XPath parse. I'm curious now what the comparison would be for Java's regexp support versus, say, Jaxen and JDOM (which is how I usually do XPath in Java). In my dabblings with timings, Java regexp's are very fast. Apparently, Tim Bray found this as well.

Here's the Perl code:


use XML::XPath;
use XML::XPath::XMLParser;
use XML::Parser;
use Benchmark qw(:all) ; 

my $X = new XML::Parser(ParseParamEnt => 0); # non-validating parsing, please

timethese(10000, {
    'xpath' => \&xpath,
    'regexp' => \&regexp

sub xpath {
    my $b = getBlog();
    my $parser = XML::XPath::XMLParser->new(parser => $X);
    my $root_node = $parser->parse($b);
    my $xp = XML::XPath->new(context => $root_node);
    my $nodeset = $xp->find('/tapi/document/result/weblog/author'); 
    die if ! defined($nodeset);

sub regexp {
    my $b = getBlog();
    my ($author) = $b =~ m{<author>(.*)</author>}sm; 
    die if ! defined($author);

sub getBlog {
    return q{<?xml version="1.0" encoding="utf-8"?>
<!-- generator="Technorati API version 1.0 /bloginfo" -->
<!DOCTYPE tapi PUBLIC "-//Technorati, Inc.//DTD TAPI 0.02//EN" "http://api.technorati.com/dtd/tapi-002.xml">
<tapi version="1.0">
    <name>What's That Noise?! [Ian Kallen's Weblog]</name>
    <lastupdate>2006-01-02 18:38:03</lastupdate>
    <created>2004-02-23 12:04:51</created>

For some of the messaging infrastructure at Technorati where the messages are real simple name/value constructs, we've been passing on using XML at all. Using a designated-character-delimited format string (say, tabs) that can be rapidly transformed into a java.util.Map (or a Perl hash, a Python dictionary, yadda yadda yea) and passing messages that way buys a lot of cheap milage. We like cheap milage.

( Jan 05 2006, 11:26:28 AM PST ) Permalink


Post a Comment:

Comments are closed for this entry.