Macro mongodm::pipeline

macro_rules! pipeline {
    ($($tt:tt)*) => { ... };
}

Helper to build aggregation pipelines. Return a Vec as expected by the aggregate function.

Example

use mongodm::prelude::*;

struct User {
    _id: ObjectId,
    name: String,
}

struct Session {
    user_id: ObjectId,
}

// Using the pipeline! helper :
let a = pipeline! [
    Match: { f!(name in User): "John" },
    Lookup {
        From: "sessions",
        As: "sessions",
        LocalField: f!(_id in User),
        ForeignField: f!(user_id in Session),
    }
];

// Without pipeline helper :
let b = vec![
    doc! { "$match": { f!(name in User): "John" } },
    Lookup {
        From: "sessions",
        As: "sessions",
        LocalField: f!(_id in User),
        ForeignField: f!(user_id in Session),
    }.into(),
];

// Without any helpers :
let c = vec![
    doc! { "$match": { "name": "John" } },
    doc! { "$lookup": {
        "from": "sessions",
        "as": "sessions",
        "localField": "_id",
        "foreignField": "user_id",
    } },
];

// Generated pipelines are identicals
assert_eq!(a, b);
assert_eq!(a, c);