Indexing serde_json::Value during query-building

[Kibouo]

I'm trying to remove expired sessions from a postgresql db.

The scheme looks like this:

table! {
    session (key) {
        key -> Uuid,
        data -> Jsonb,
    }
}

And the table as follows:

#[derive(Queryable, Insertable, AsChangeset)]
#[table_name = "session"]
pub struct Session
{
    pub key:  ::uuid::Uuid,
    pub data: ::serde_json::Value
}

The data field is always filled in using following (to-be extended) struct:

use chrono::{DateTime, Utc};
pub struct SessionData
{
    pub deadline: DateTime<Utc>
}

I wanted to index the data.deadline aka SessionData.deadline field, and delete expired sessions as such:

diesel::delete(session.filter(data["deadline"].st(now))).execute(&*db_conn)

This doesn't work. It returns the compile-error

error[E0608]: cannot index into a value of type `db::schema::session::session::columns::data`
  --> web/src/main.rs:65:55
   |
65 |                         diesel::delete(session.filter(data["deadline"].st(now)))
   |                                                       ^^^^^^^^^^^^^^^^

How can this be done? I can't seem to find any documentation that uses indexing in a query.

Versions

• Rust: rustc 1.30.0-nightly (73c78734b 2018-08-05)
• Diesel: "1.3.2"
• serde: "1.0.70"
• serde_json: "1.0.24"
• Database: postgresql 10.5
• Operating System: Arch Linux x86_64 4.17.12-arch1-1-ARCH

Feature Flags

• diesel: "postgres", "r2d2", "serde_json", "uuid"

[sgrif]

#44 tracks json operator support

[Kibouo]

At the time of asking this question, json operators are not implemented yet. A work-around is using sql() to write raw SQL code.