As both a stress test and to experiment, I created a database using a recent complete (current page) dump of English Wikipedia, a hefty file of 30.5 GB. I don&#39;t have enough memory apparently to create a full-text index of all of that text, so I created the DB without one.<div>

<br></div><div>My first testing came up empty until I realized that I needed to deal with the namespace (ugh). Then I tried:</div><div><br></div><div><div>declare default element namespace &quot;<a href="http://www.mediawiki.org/xml/export-0.4/">http://www.mediawiki.org/xml/export-0.4/</a>&quot;;</div>
<div>//siteinfo</div></div><div><br></div><div>This contains a small amount of data and occurs only once in the document (at /mediawiki/siteinfo). However, it&#39;s extremely slow (~33 seconds on my system). The query plan is:</div>
<div><br></div><div><div>&lt;IterPath&gt;</div><div>  &lt;Root/&gt;</div><div>  &lt;IterStep axis=&quot;child&quot; test=&quot;*:mediawiki&quot;/&gt;</div><div>  &lt;IterStep axis=&quot;child&quot; test=&quot;*:siteinfo&quot;/&gt;</div>
<div>&lt;/IterPath&gt;</div></div><div><br></div><div><div>Timing:</div><div> - Parsing:  0.35 ms</div><div> - Compiling:  0.22 ms</div><div> - Evaluating:  33316.32 ms</div><div> - Printing:  0.3 ms</div><div> - Total Time:  33317.19 ms</div>
</div><div><br></div><div><br></div><div>My surmise is that millions of node names are being checked rather than a path index being used to rapidly access the appropriate node(s). I don&#39;t think such a simple query should fail to be properly optimized. Another surmise is that it&#39;s related to namespaces not being indexed (?). While personally I very much dislike namespaces, they are common, and they have to be efficiently handled.</div>
<div><br></div><div>To see if it made a difference, I also tried an explicitly named namespace test:</div><div><br></div><div><div>declare namespace w=&quot;<a href="http://www.mediawiki.org/xml/export-0.4/">http://www.mediawiki.org/xml/export-0.4/</a>&quot;;</div>
<div>//w:siteinfo</div></div><div><br></div><div>This results in:</div><div><br></div><div><div>&lt;IterPath&gt;</div><div>  &lt;Root/&gt;</div><div>  &lt;IterStep axis=&quot;descendant&quot; test=&quot;w:siteinfo&quot;/&gt;</div>
<div>&lt;/IterPath&gt;</div><div>Timing:</div><div> - Parsing:  0.33 ms</div><div> - Compiling:  0.07 ms</div><div> - Evaluating:  54288.51 ms</div><div> - Printing:  0.3 ms</div><div> - Total Time:  54289.23 ms</div></div>
<div><br></div><div>So performance is even worse.</div><div>
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