Bulk delete - performance / object collection

I'm trying to bulk-delete several million rows from my database.

The docs for Django 1.3 say "this will, whenever possible, be executed purely in SQL". A pure-SQL delete is what I want in this case, so that's fine.

However, the code is never getting as far as running any SQL.

Interrupting the script shows that the delete method on the QuerySet is trying to use a "Collector" to construct model instances for each row I'm trying to delete. This is going to take too long (and may in fact consume all the memory available) -- I don't think it's practical to wait in this case. (I've tried waiting over half an hour!)

(I'm looking at django.db.models.query.QuerySet.delete and django.db.models.deletion.Collector.collect / Collector.add.)

What's the point in doing the delete "purely in SQL" if all of the objects are getting constructed anyway? Why do they need to be "collected" before the SQL DELETE is run? The model instance in this case has no child rows, to which the delete might need to be cascaded.

Meanwhile I can construct the SQL by hand easily enough, but I feel this isn't doing things the right way.

thanks for any help

George

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