Reference QuerySet API reference

select_related(*fields) Returns a QuerySet that will join in the named foreign-key relationships, selecting additional related objects when it executes its query.

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Reference QuerySet API reference QuerySet APIMethods that return new QuerySets

select_related(*fields) Returns a QuerySet that will “follow” foreign-key relationships, selecting additional related-object data when it executes its query.

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Topic guide Database access optimization

When the FETCH_PEERS fetch mode is not appropriate or efficient enough, use select_related() and prefetch_related(). Understand their documentation thoroughly and apply them where needed. It may be useful to apply these methods in managers and default managers.

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Topic guide Database access optimization Retrieve everything at once if you know you will need it

Understand select_related() and prefetch_related() thoroughly, and use them: in managers and default managers where appropriate. Be aware when your manager is and is not used; sometimes this is tricky so don’t make assumptions.

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Reference QuerySet API reference QuerySet APIMethods that return new QuerySets

This has a similar purpose to select_related, in that both are designed to stop the deluge of database queries that is caused by accessing related objects, but the strategy is quite different.

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Reference QuerySet API reference

This method has a similar purpose to select_related(), in that both are designed to eagerly fetch related objects. However, they work in different ways.

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Reference QuerySet API reference

For example, rows of related objects specified in select_related() are locked in addition to rows of the queryset’s model. If this isn’t desired, specify the related objects you want to lock in select_for_update(of=(...)) using the same fields syntax as select_related().

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Topic guide Making queries

These accessors may be prefetched by the QuerySet methods select_related() or prefetch_related(). If not prefetched, access will trigger an on-demand fetch through the model’s fetch mode.

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Reference QuerySet API reference QuerySet APIMethods that return new QuerySets

For example, rows of related objects specified in select_related() are locked in addition to rows of the queryset’s model. If this isn’t desired, specify the related objects you want to lock in select_for_update(of=(...)) using the same fields syntax as select_related().

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Reference The Django admin site ModelAdmin objects

By default, this is set to 100. ModelAdmin.list_select_related : Set list_select_related to tell Django to use select_related() in retrieving the list of objects on the admin change list page. This can save you a bunch of database queries.

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Reference QuerySet API reference Query-related tools

… a base QuerySet for the given lookup. This is useful to further filter down the prefetch operation, or to call select_related() from the prefetched relation, hence reducing the number of queries even further: The to_attr argument sets the result of …

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Topic guide Making queries Related objectsOne-to-many relationships

Subsequent accesses to the foreign key on the same object instance are cached. Example: Note that the select_related() QuerySet method recursively prepopulates the cache of all one-to-many relationships ahead of time. Example:

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Design philosophies Database API

This is also why the select_related() QuerySet method exists. It’s an optional performance booster for the common case of selecting “every related object.”

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Reference The Django admin site ModelAdmin objects

ModelAdmin.get_list_select_related(request)[source] : The get_list_select_related method is given the HttpRequest and should return a boolean or list as ModelAdmin.list_select_related does.

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Reference QuerySet API reference

… a base QuerySet for the given lookup. This is useful to further filter down the prefetch operation, or to call select_related() from the prefetched relation, hence reducing the number of queries even further: The to_attr argument sets the result of …

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Reference The Django admin site

By default, this is set to 100. ModelAdmin.list_select_related : Set list_select_related to tell Django to use select_related() in retrieving the list of objects on the admin change list page. This can save you a bunch of database queries.

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Topic guide Database access optimization

Enable it for all usage of your models with a custom manager. Using this fetch mode is easier than declaring fields to fetch with select_related() or prefetch_related(), especially when it’s hard to predict which fields will be accessed.

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Topic guide Making queries

Subsequent accesses to the foreign key on the same object instance are cached. Example: Note that the select_related() QuerySet method recursively prepopulates the cache of all one-to-many relationships ahead of time. Example:

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Index

… django.middleware.security) - seekable() (HttpResponse method) - Select (class in django.forms) - select_for_update() (in module django.db.models.query.QuerySet) - select_on_save (Options attribute) - select_related() (in module django.db.models.query.QuerySet) - select_template() (Engine method) - (in module django.template.loader) - SelectDateWidget (class in django.forms) - SelectMultiple (class …

Internals Django Deprecation Timeline

Calling QuerySet.select_related() without arguments will raise TypeError. QuerySet.select_related() will raise TypeError if passed True rather than AttributeError. ModelAdmin will raise ValueError if subclassed with its list_select_related attribute set to True. ModelAdmin will raise ValueError if its get_list_select_related() method returns True.

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