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Each time the save() method is called on a Django object, Django executes two queries one INSERT and one SELECT. In my case this is usefull except for some specific places where each query is expensive. Any ideas on how to sometimes state that no object needs to be returned - no SELECT needed.

Also I'm using django-mssql to connect to, this problem doesn't seem to exist on MySQL.

EDIT : A better explanation

h = Human()
h.name='John Foo'
print h.id # Returns None, No insert has been done therefore no id is available
h.save()
print h.id # Returns the ID, an insert has taken place and also a select statement to return the id

Sometimes I don't the need the retruning ID, just insert

Siavash
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    Well, that's strange, MSSQL supports [`INSERT...OUTPUT`](http://msdn.microsoft.com/en-us/library/ms177564.aspx) so I don't see why it would issue two queries, but then again I am not that familiar with `django-mssql`. Perhaps you could build your own INSERT statements for expensive queries? – Davor Lucic Jun 07 '11 at 10:35

3 Answers3

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Try to use save() method with force_insert or force_update attributes. With this attributes django knows about record existence and don't make additional query.

40ins
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  • The problem's not whether django checks for exsistance or not, it's the fact that after every `INSERT` it runs a `SELECT` statement just to keep the objects `id` handy. – Siavash Jun 12 '11 at 08:26
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40ins's answer was right, but probably it might have higher costs...

When django execustes a save(), it needed to be sure if the object is a new one or an existing one. So it hits the database to check if related objext exists. If yes, it executes an UPDATE, orherwise it executes an ISERT

Check documentatin from here...

You can use force_insert or force_update ,but that might be cause serious data integrity problems, like creating a duplicate entry instead of updating the existing one...

So, if you wish to use force , you must be sure whether it will be an INSERT or an UPDATE...

Mp0int
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The additional select is the django-mssql backend getting the identity value from the table to determine the ID that was just inserted. If this select is slow, then something is wrong with your SQL server/configuration because it is only doing SELECT CAST(IDENT_CURRENT(*table_name*) as bigint) call.

Manfre
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