Cut Final Character

Grundformeintrag even when cutting final character (f in this case)
Why is this query slow when I include fields from p2 or c2?

SQL

USE dewiktionary_p;
SELECT CONCAT('# [[',p1.page_title,']]') AS page_title,
p1.page_id,
p1.page_namespace,
cl_from,
cl_to,
# p2.page_title,
# p2.page_id,
# p2.page_namespace
FROM page p1
JOIN categorylinks
ON cl_from = p1.page_id
# JOIN page p2
# ON cl_to = p2.page_title 
# AND p2.page_namespace = 14
#LEFT JOIN page_props
#ON p2.page_id = pp_page AND pp_propname = 'hiddencat'
WHERE p1.page_namespace = '(main)'
AND p1.page_is_redirect = 0
# AND p1.page_title REGEXP '^Haus$';
AND p1.page_title = 'Käse'
and cl_to = 'Substantiv_(Deutsch)';

SQL

Checking query status...