Wrong SELECT syntax breaks db_rewrite_sql

I found my apache log flooded with warnings. On closer inspection looks like db_rewrite_sql inserts DISTINCT where it does not belong (inside LEFT JOIN statement). Here is rewritten SQL out of the logfile:

SELECT ht.* 
FROM node n 
	LEFT JOIN helptip ht ON ht.DISTINCT(n.nid) = n.nid 
	LEFT JOIN helptip_user_data ht_hidden ON ht_hidden.uid=0 AND ht_hidden.nid=n.nid AND ht_hidden.relation='hidden'  
	INNER JOIN node_access na ON na.nid = n.nid  
WHERE 	(na.grant_view >= 1 AND ((na.gid = 0 AND na.realm = 'all') OR 
	(na.gid = 0 AND na.realm = 'og_public') OR 
	(na.gid = 0 AND na.realm = 'og_all'))) AND 
		n.status = 1 AND 
		ht_hidden.relation IS NULL AND 
		('node/28189' LIKE ht.path OR 'feed/items/system/2007/03/13/borat_from_the_cutting_room_floor' LIKE ht.path) AND 
		weight >= -10 AND weight <= 10 

ORDER BY ht.weight, RAND() LIMIT 1 

The problem is regular expression in db_distinct_field, which does not understand the SQL fed to it by helptip. The fix is trivial tweak of one line where SELECT statement is:

Original code (excerpt):

    $result = db_query(db_rewrite_sql("SELECT ht.* FROM {node} n ...

Replacement code:

    $result = db_query(db_rewrite_sql("SELECT nid FROM {node} n ...

Attached module file can be commited to 4.7. This still needs to be propagated into 5.0.