Trying to implement a way to change schema at runtime

[Datron]

cargo version: cargo 1.80.0 (376290515 2024-07-16)
rust version: rustc 1.80.1 (3f5fd8dd4 2024-08-06) (built from a source tarball)

Hi Diesel Team,

I'm trying to build a way to change the table schema at runtime. This is to support a multi-tenant setup for a project I'm working on. Earlier I was setting the search path in the connection string and pooling these connections for a particular tenant, but as the number of tenants have increased; I have reached the max number of connections I can make to my postgres instance.

I tried following the advice in this thread and got an implementation done, but I can't get it to work. I get the error:

the method `select` exists for struct `PgSchema<table>`, but its trait bounds were not satisfied
the following trait bounds were not satisfied:
`&PgSchema<table>: Table`
which is required by `&PgSchema<table>: QueryDsl`
`&mut PgSchema<table>: Table`
which is required by `&mut PgSchema<table>: QueryDsl`

Not sure what I am missing here. Am I on the right track? I'm looking for guidance and suggestions and how I can implement this correctly.
Example

[Datron]

Some info on diesel integration
version = "2.1.2"
features = ["postgres", "postgres_backend", "r2d2", "chrono", "uuid"]

[weiznich]

As listed in the documentation SelectDsl is only implemented for 4 types. Your PgSchema type is neither one of the 4 concrete types nor does it implement Table as required by the fourth impl.

You have two options to fix that: Either implement Table or manually implement SelectDsl.

[Datron]

@weiznich I have implemented SelectDsl here but it doesn't work, I get the same error. How would I get this to work with Inserts as well? I don't see a InsertDsl trait.

I tried implementing the trait Table on my struct PgSchema, but this results in an issue where the compilation of my code never terminates.

[Datron]

If I import diesel::query_dsl::select_dsl::SelectDsl into the file and then try to select on a PgSchema type, I get

error[E0599]: the method `select` exists for struct `PgSchema<table>`, but its trait bounds were not satisfied
   --> example/src/main.rs:129:10
    |
128 |       let test_one_records = _users_schema
    |  ____________________________-
129 | |         .select(username)
    | |         -^^^^^^ method cannot be called on `PgSchema<table>` due to unsatisfied trait bounds
    | |_________|
    |
    |
    = note: the following trait bounds were not satisfied:
            `&PgSchema<table>: Table`
            which is required by `&PgSchema<table>: QueryDsl`
            `&PgSchema<table>: Table`
            which is required by `&PgSchema<table>: SelectDsl<_>`
            `&PgSchema<table>: Query`
            which is required by `&PgSchema<table>: SelectDsl<_>`
            `&PgSchema<table>: SelectDsl<_>`
            which is required by `&PgSchema<table>: SelectDsl<_>`
            `&mut PgSchema<table>: Table`
            which is required by `&mut PgSchema<table>: QueryDsl`
            `&mut PgSchema<table>: Table`
            which is required by `&mut PgSchema<table>: SelectDsl<_>`
            `&mut PgSchema<table>: Query`
            which is required by `&mut PgSchema<table>: SelectDsl<_>`
            `&mut PgSchema<table>: SelectDsl<_>`
            which is required by `&mut PgSchema<table>: SelectDsl<_>`

I'm wondering if I have to implement SelectDsl for all references to PgSchema or is there any other way?

[Datron]

Hey @weiznich , any ideas on what I could do here? I'm still stuck on this

[weiznich]

I've not forgotten about this, but I just don't have the capacity to provide an answer. After all this is still a free time project, so answering support question is something that needs to wait until I have time. If you need a more timely support channel you would need to think about a support contract.

[Datron]

Sure, thanks for your time. Just wanted to check in and see if you have any inputs.