Thursday January 05, 2006

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) 

Here's the Perl code:

#!/usr/bin/perl

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">
<document>
<result>
  <url>http://www.arachna.com/roller/page/spidaman</url>
  <weblog>
    <name>What's That Noise?! [Ian Kallen's Weblog]</name>
    <url>http://www.arachna.com/roller/page/spidaman</url>
    <rssurl>http://www.arachna.com/roller/rss/spidaman</rssurl>
    <atomurl></atomurl>
    <inboundblogs>6</inboundblogs>
    <inboundlinks>8</inboundlinks>
    <lastupdate>2006-01-02 18:38:03</lastupdate>
    <lastupdate-unixtime>1136255883</lastupdate-unixtime>
    <created>2004-02-23 12:04:51</created>
    <created-unixtime>1077566691</created-unixtime>
    <rank>false</rank>
    <lat>0.0</lat>
    <lon>0.0</lon>
    <lang>26110</lang>
    <author>
      <username>spidaman</username>
      <firstname>Ian</firstname>
      <lastname>Kallen</lastname>
      <thumbnailpicture>http://static.technorati.com/progimages/photo.jpg?uid=11648</thumbnailpicture>
    </author>
  </weblog>
  <inboundblogs>6</inboundblogs>
  <inboundlinks>8</inboundlinks>
</result>
</document>
</tapi>
};
}

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.

xpath regexp perl java messaging technorati