Optmized Query

[Soumen Khatua]

Hi Folks,

I have many to many relationships and Foreign Key in the table, I'm using select_realted(foreign key filed name) to optimize the query but I want to fetch many to many and foreign key at the same time , How I can do this in very optimized way?

Thank You

Regards,

Soumen

[Chetan Ganji]

select_related for fk and prefetch_related for m2m in django, you can chain them together 

Regards,

Chetan Ganji

+91-900-483-4183

ganji....@gmail.com

http://ryucoder.in

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[Soumen Khatua]

I also know about this concept but I don't how I can achieve it, Could you give me an example?
Suppose I have:

class Profile(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        on_delete = models.CASCADE,
        related_name="profile"
    )
    location = models.ManyToManyField(Location)

Thank you

Regards,

Soumen

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[Chetan Ganji]

Profile.objects.filter().select_related("user").prefetch_related("location")

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[Soumen Khatua]

Now I'm facing one problem whenever I'm trying to iterate a loop I'm getting too many SQL variables. Actually after iterating the loop I want to render all the value in the template.
if could you resolve this it would be very good for me.
Thank you for your time and response

Regards,
Soumen

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[Soumen Khatua]

Actually I want to fetch all users from User table and users location from Location table which is many to many relation from same Profile table. Is it possible??? 

[אורי‎]

Hi Soumen,

Sometimes prefetch_related is much faster and more efficient than select_related. I usually prefer to use prefetch_related.

Uri.

אורי

u...@speedy.net

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[Sencer Hamarat]

I thought select_related works for only FK/M2M and prefetch_related works for only reverse relations, doesn't it?

Saygılarımla,

Sencer HAMARAT

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[אורי‎]

They both work for both.

אורי

u...@speedy.net

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[Soumen Khatua]

Hi,

Yeah, but whenever I'm trying to iterate a loop on all these qs. I'm getting an error too many sql variables. I know I'm doing something wrong,but I'm not able to find the error.

Thank you for your response and time.

Regards,

Soumen

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