placeholder confusion when using aggregated query with extra

[slide21@…]

Let's assume something like this:

Book.objects.extra(select={'date': "DATE_FORMAT(timestamp, '%s')"}, select_params=('%%H',), where=["DATE_FORMAT(timestamp, '%%H:%%i') > '%s'"], params=['22:00']).values('date').annotate(cnt=Count('id'))

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the resulting sql query is:

SELECT DATE_FORMAT(timestamp, '%H') AS `date`, COUNT(id) AS `cnt` FROM `books` WHERE DATE_FORMAT(timestamp, '%H:%i') > '%H' GROUP BY DATE_FORMAT(timestamp, '22:00') ORDER BY timestamp ASC

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the placeholder values '%H' and '22:00' are interchanged, which is obviously a result of using the GROUP BY here on a user-defined variable with placeholder (--> 'date')

.query.as_sql() gives something like

(u"SELECT DATE_FORMAT(timestamp, '%s') AS `date`, COUNT(id) AS `cnt` FROM `books` WHERE DATE_FORMAT(timestamp, '%H:%i') > '%s' GROUP BY DATE_FORMAT(timestamp, '%s') ORDER BY timestamp ASC", (u'%H', u'%H', u'22:00'))

[Russell Keith-Magee]

I'm going to close this as a dupe of #11104. It's not a literal duplicate - the problem that is being described is different - but the underlying cause (mishandling of SQL params) is the same. I'll put a link on #11104 to ensure that this problem is also fixed.