How can I use prefetch_related in self related model

I have Menu model which has ForeignKey named parent related with itself.

If parent is None it means this menu is parent menu if it shows another Menu object it means it is submenu for its parent(many-to-one relation)

Here is my problem, I want to get all menus with its submenus using prefetch_related, How can I do it?

Note: I do not want to get submenus going database each time in for
menu

Here is my model class

class Menu(models.Model):

    title = models.CharField(max_length=30)

    language = models.ForeignKey(Language)

    parent = models.ForeignKey("self", default=None, blank=True, null=True, related_name="submenus")

Here is my query

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).prefetch_related("submenus").order_by("order")

for p in pm2:

    print(p.title)

    print(p.submenus)

When I print the submenus the result is app.Menu.None

edited Feb 27 '18 at 7:43

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

Your model doesn't mention submenus at all, so I would expect .prefetch_related("submenus") to give an error. Will your submenus have their own submenus, or will your menus only have two levels? If you have multiple levels, then you may want to look at django-mptt.

– Alasdair
Feb 26 '18 at 15:41

django-mptt is hopelessly convoluted to work with. I would suggest using materialized paths instead (e.g. communities.bmc.com/docs/DOC-9902)

– thebjorn
Feb 26 '18 at 15:54

add a comment |

I have Menu model which has ForeignKey named parent related with itself.

If parent is None it means this menu is parent menu if it shows another Menu object it means it is submenu for its parent(many-to-one relation)

Here is my problem, I want to get all menus with its submenus using prefetch_related, How can I do it?

Note: I do not want to get submenus going database each time in for
menu

Here is my model class

class Menu(models.Model):

    title = models.CharField(max_length=30)

    language = models.ForeignKey(Language)

    parent = models.ForeignKey("self", default=None, blank=True, null=True, related_name="submenus")

Here is my query

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).prefetch_related("submenus").order_by("order")

for p in pm2:

    print(p.title)

    print(p.submenus)

When I print the submenus the result is app.Menu.None

edited Feb 27 '18 at 7:43

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

Your model doesn't mention submenus at all, so I would expect .prefetch_related("submenus") to give an error. Will your submenus have their own submenus, or will your menus only have two levels? If you have multiple levels, then you may want to look at django-mptt.

– Alasdair
Feb 26 '18 at 15:41

django-mptt is hopelessly convoluted to work with. I would suggest using materialized paths instead (e.g. communities.bmc.com/docs/DOC-9902)

– thebjorn
Feb 26 '18 at 15:54

add a comment |

I have Menu model which has ForeignKey named parent related with itself.

If parent is None it means this menu is parent menu if it shows another Menu object it means it is submenu for its parent(many-to-one relation)

Here is my problem, I want to get all menus with its submenus using prefetch_related, How can I do it?

Note: I do not want to get submenus going database each time in for
menu

Here is my model class

class Menu(models.Model):

    title = models.CharField(max_length=30)

    language = models.ForeignKey(Language)

    parent = models.ForeignKey("self", default=None, blank=True, null=True, related_name="submenus")

Here is my query

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).prefetch_related("submenus").order_by("order")

for p in pm2:

    print(p.title)

    print(p.submenus)

When I print the submenus the result is app.Menu.None

edited Feb 27 '18 at 7:43

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

I have Menu model which has ForeignKey named parent related with itself.

If parent is None it means this menu is parent menu if it shows another Menu object it means it is submenu for its parent(many-to-one relation)

Here is my problem, I want to get all menus with its submenus using prefetch_related, How can I do it?

Note: I do not want to get submenus going database each time in for
menu

Here is my model class

class Menu(models.Model):

    title = models.CharField(max_length=30)

    language = models.ForeignKey(Language)

    parent = models.ForeignKey("self", default=None, blank=True, null=True, related_name="submenus")

Here is my query

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).prefetch_related("submenus").order_by("order")

for p in pm2:

    print(p.title)

    print(p.submenus)

When I print the submenus the result is app.Menu.None

django django-models django-orm

edited Feb 27 '18 at 7:43

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

edited Feb 27 '18 at 7:43

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

edited Feb 27 '18 at 7:43

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

asked Feb 26 '18 at 15:30

Selim Yılmaz

23627

Your model doesn't mention submenus at all, so I would expect .prefetch_related("submenus") to give an error. Will your submenus have their own submenus, or will your menus only have two levels? If you have multiple levels, then you may want to look at django-mptt.

– Alasdair
Feb 26 '18 at 15:41

django-mptt is hopelessly convoluted to work with. I would suggest using materialized paths instead (e.g. communities.bmc.com/docs/DOC-9902)

– thebjorn
Feb 26 '18 at 15:54

add a comment |

Your model doesn't mention submenus at all, so I would expect .prefetch_related("submenus") to give an error. Will your submenus have their own submenus, or will your menus only have two levels? If you have multiple levels, then you may want to look at django-mptt.

– Alasdair
Feb 26 '18 at 15:41

django-mptt is hopelessly convoluted to work with. I would suggest using materialized paths instead (e.g. communities.bmc.com/docs/DOC-9902)

– thebjorn
Feb 26 '18 at 15:54

Your model doesn't mention submenus at all, so I would expect .prefetch_related("submenus") to give an error. Will your submenus have their own submenus, or will your menus only have two levels? If you have multiple levels, then you may want to look at django-mptt.

– Alasdair
Feb 26 '18 at 15:41

django-mptt is hopelessly convoluted to work with. I would suggest using materialized paths instead (e.g. communities.bmc.com/docs/DOC-9902)

– thebjorn
Feb 26 '18 at 15:54

add a comment |

1 Answer
1

active

oldest

votes

You don't need to use prefetch_related since this is used for many-to-many relationships, instead, you can use select_related.

So your query would be

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).select_related("submenus").order_by("order")

answered Nov 24 '18 at 0:14

Rada

711315

Sorey for late response. In here i think i need to use prefetch_related because i want to get submenus and submenus is the reverse ForeignKeys "parent" field.

– Selim Yılmaz
Dec 28 '18 at 8:49

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

You don't need to use prefetch_related since this is used for many-to-many relationships, instead, you can use select_related.

So your query would be

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).select_related("submenus").order_by("order")

answered Nov 24 '18 at 0:14

Rada

711315

Sorey for late response. In here i think i need to use prefetch_related because i want to get submenus and submenus is the reverse ForeignKeys "parent" field.

– Selim Yılmaz
Dec 28 '18 at 8:49

add a comment |

You don't need to use prefetch_related since this is used for many-to-many relationships, instead, you can use select_related.

So your query would be

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).select_related("submenus").order_by("order")

answered Nov 24 '18 at 0:14

Rada

711315

Sorey for late response. In here i think i need to use prefetch_related because i want to get submenus and submenus is the reverse ForeignKeys "parent" field.

– Selim Yılmaz
Dec 28 '18 at 8:49

add a comment |

You don't need to use prefetch_related since this is used for many-to-many relationships, instead, you can use select_related.

So your query would be

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).select_related("submenus").order_by("order")

answered Nov 24 '18 at 0:14

Rada

711315

You don't need to use prefetch_related since this is used for many-to-many relationships, instead, you can use select_related.

So your query would be

pm2 = Menu.objects.filter(parent=None, language__code=language, menutype=menutype).select_related("submenus").order_by("order")

answered Nov 24 '18 at 0:14

Rada

711315

answered Nov 24 '18 at 0:14

Rada

711315

answered Nov 24 '18 at 0:14

Rada

711315

answered Nov 24 '18 at 0:14

Rada

711315

Sorey for late response. In here i think i need to use prefetch_related because i want to get submenus and submenus is the reverse ForeignKeys "parent" field.

– Selim Yılmaz
Dec 28 '18 at 8:49

add a comment |

Sorey for late response. In here i think i need to use prefetch_related because i want to get submenus and submenus is the reverse ForeignKeys "parent" field.

– Selim Yılmaz
Dec 28 '18 at 8:49

Sorey for late response. In here i think i need to use prefetch_related because i want to get submenus and submenus is the reverse ForeignKeys "parent" field.

– Selim Yılmaz
Dec 28 '18 at 8:49

add a comment |

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