Walled gardens

SQL

SET @ARTICLE_SPACE = 0;

# this finds cycles of 3 articles
select p1.page_title as 'page_1', p2.page_title as 'page_2', p3.page_title as 'page_3'
from page as p1
join page as p2 on p2.page_title in (select pl_title from pagelinks where pl_from=p1.page_id)
join page as p3 on p3.page_title in (select pl_title from pagelinks where pl_from=p2.page_id)
where p1.page_title in (select pl_title from pagelinks where pl_from=p3.page_id)
and p1.page_namespace =  @ARTICLE_SPACE and p2.page_namespace =  @ARTICLE_SPACE and p3.page_namespace =  @ARTICLE_SPACE
and not p1.page_is_redirect and not p2.page_is_redirect and not p3.page_is_redirect
limit 1;
SQL

Checking query status...
