如何在Go中的AppEngine的数据存储区中建立多对多关系？

Question

I'm trying to wrap my head around how I can represent a many-to-many relationship inside of AppEngine's Datastore in the Go Programming Language. I'm more used to traditional relational databases.

I have two types of entities in my system. Let's call them A and B. Every A entity is related to some number of B entities. Similarly, every B entity is related to some other number of A entities. I'd like to be able to efficiently query for all B entities given an A entity, and for all A entities given a Bentity.

In the Python SDK, there seems to be a way to note fields in an entity can be ReferencePropertys which reference some other entity. However, I can't find something similar in Go's AppEngine SDK. Go seems to just use basic structs to represent entities.

What's the best practice for dealing with this?

Answer 1

based on how you which to query you could do the following:

in your struct A add a field:

BIds []int64

in your struct B add a field:

AIds []int64

now any time you add a relation between A and B you just need to add the corresponding ids to your two variables

when you need to query now for all B which are related to this A1 you do your query like this:

SELECT * FROM B where AIds = 'A1'

for all A wich are related to this B1 your do it similar:

SELECT * FROM A where BIds = 'B1'

update:
altered querys on suggestion from dragonx