On Sun, Jul 19, 2009 at 9:51 PM, aXqd<axqd...@gmail.com> wrote:
>
> Hi, all:
>
> I encountered another redundant SQL query problem while using django.
> And this time it might even cause a defect of my own program.
>
> Here is the thing. I want to do something like below:
> FOO.objects.filter( bar_id__exact = 5 ).delete()
>
> But what I got from mysql log are:
>
> 1 SELECT blahblahblah... FROM `foo` WHERE (`foo`.`bar_id` = 5 ) LIMIT 100
> 2 DELETE FROM `foo` WHERE `id` IN (7, 10, 13)
> 3 commit
> 4 SELECT blahblahblah... FROM `foo` WHERE (`foo`.`bar_id` = 5 ) LIMIT 100
>
> Questions are:
> 1. For Line 1, why it LIMITed the number of results to 100 while i'm
> hoping to delete them all?
> 2. For Line 1 and 2, is there any way to do "DELETE FROM 'foo' WHERE
> ('foo'.'bar_id' = 5)"?
> I think this is a quite common scenario.
> 3. For Line 4, is that a double check? Why would I need this query?
>
> I'm new to django, thanks for all your kind help.
>
> --
> Regards.
> -Tian
>
> >
>
The reason for this is Django emulates DELETE ON CASCADE behavior,
which means doing some pure python processing. However, I believe
that last SELECT query should be able to be optimized out, so I'm
going to look into removing it.
Alex
--
"I disapprove of what you say, but I will defend to the death your
right to say it." -- Voltaire
"The people's good is the highest law." -- Cicero
"Code can always be simpler than you think, but never as simple as you
want" -- Me
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