When CustomHeader is enabled (see CustomHeader from HTTPHeaderSettings group in site.ini), the same query is run two times on each page.

The query looks like:
SELECT e0.id AS e0_id, e0.link AS e0_link, e0.text AS e0_text, e0.text_md5 AS e0_text_md5, e0.action AS e0_action, e0.is_alias AS e0_is_alias
FROM ezurlalias_ml AS e0
WHERE e0.parent = 0 AND (e0.lang_mask & 3 > 0) AND e0.text_md5 = MD5( 'yoururl' )
LIMIT 0, 1

and is produced by eZURLAliasML::translate()

The first query occurs in kernel/classes/ezhttpheader.php:106 and the second in index.php:533.

Steps to reproduce

override site.ini and put :

[HTTPHeaderSettings]
CustomHeader=enabled

then activate SQL debug output

load a page and see...