How to make a filter query across all tenants ignoring the namespace of each tenant (i.e. a query with WILDCARD namespace ) in objectify

[Baqir Rizvi]

I have a multitenant application in which each school is a tenant. Each school can have many teachers. So I have two kind of entity one is "School" and second is "Teacher" such that each teacher has a parent school. I am using @Parent annotation of objectify for building the relationship between school and teacher.

Now I want to count the number of teachers across the schools for my admin portal.Is there any concept of global namespace in objectify/datastore?

[Jeff Schnitzer]

This is the problem with namespaces, and why I tell everyone: Don’t use them, ever. Just model your data normally. If you want to query the teachers for a school, you can do that without namespaces. On the other hand, as soon as you want to do a cross-namespace query, you’re screwed.

Jeff

On Fri, Nov 4, 2016 at 12:00 AM, Baqir Rizvi <baqir.g...@gmail.com> wrote:

I have a multitenant application in which each school is a tenant. Each school can have many teachers. So I have two kind of entity one is "School" and second is "Teacher" such that each teacher has a parent school. I am using @Parent annotation of objectify for building the relationship between school and teacher.

Now I want to count the number of teachers across the schools for my admin portal.Is there any concept of global namespace in objectify/datastore?

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[Baqir Rizvi]

Thanks for replying Jeff. When you do things by yourself then things become more clear with pros and cons. I wonder why there is no concept of global namespace.
Currently I am running queries on each namespace. one query for getting all the namespaces and then multiple queries for getting teacher in that namespace. Assuming there are 100 tenants(school) , in worst case I need to make 1+100 query , if I am not wrong. Assuming there are many other things that my admin portal need to show which requires these kind of queries, there are following questions-
questions:

1. what possible issues these kind methods(queries on each namespace) can results, in terms of performance, leakage, security etc(anything else that I don't know).
   
2. Is there any other method solve this problem assuming that multitenancy is enable.
   

[Jeff Schnitzer]

Just put an indexed Key<?> field “school” on your Teacher. Then query teachers filtering by school (or not, if you want a global query). Namespaces are madness. N queries will perform horribly.

Pretend the namespace feature does not exist. It was a terrible idea for exactly this reason.

Jeff

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[Chuck Wight]

Jeff - Thanks for the sage advice: Don't use namespaces, ever.

The ONE attractive feature of namespaces is that it guarantees uniqueness because two (or more) properties are combined into a single key. What is the best way to guarantee uniqueness if the entities are modeled normally? That is, how should I best prevent accidental creation of a duplicate school/teacher entity?

[Jeff Schnitzer]

In the olde days you had to either use a unique natural key, or create a second entity whose primary key is the unique natural key (ie id: "school-teacher" or even {parent: "theschool", id: "theteacher"}).

However, datastore queries are now strongly consistent. So in a transaction, query for the pre-existence of your duplicate (the traditional way) and if it already exists, don't create it. Just like a normal RDBMS.

Jeff

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