On Mon, Jul 20, 2009 at 12:00 PM, Alex Gaynor<alex.gay...@gmail.com> wrote:
>
> 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
>
> >
>
Thanks, Alex.
But even if I don't care about the performance, can I be sure that
the following clause will remove all the satisfied items? or just the
first 100 ones?
FOO.objects.filter( bar_id__exact = 5 ).delete()
--
Regards.
-Tian
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