聚合表达式操作

var month = current().getDate("date").month(of("UTC"));
var precip = current().getInteger("precipitation");
asList(group(
    month,
    avg("avgPrecipMM", precip.multiply(25.4))
));

[ { $group: {
    _id: { $month: "$date" },
    avgPrecipMM: {
        $avg: { $multiply: ["$precipitation", 25.4] } }
} } ]

var showtimes = current().<MqlDocument>getArray("showtimes");
asList(project(fields(
    computed("availableShowtimes", showtimes
        .filter(showtime -> {
            var seats = showtime.<MqlInteger>getArray("seats");
            var totalSeats = seats.sum(n -> n);
            var ticketsBought = showtime.getInteger("ticketsBought");
            var isAvailable = ticketsBought.lt(totalSeats);
            return isAvailable;
        }))
)));

[ { $project: {
    availableShowtimes: {
        $filter: {
            input: "$showtimes",
            as: "showtime",
            cond: { $lt: [ "$$showtime.ticketsBought", { $sum: "$$showtime.seats" } ] }
    } }
} } ]

var temperature = current().getInteger("temperature");
asList(project(fields(
    computed("extremeTemp", temperature
        .lt(of(10))
        .or(temperature.gt(of(95))))
)));

[ { $project: {
    extremeTemp: { $or: [ { $lt: ["$temperature", 10] },
                          { $gt: ["$temperature", 95] } ] }
} } ]

var location = current().getString("location");
asList(match(expr(location.eq(of("California")))));

[ { $match: { location: { $eq: "California" } } } ]

var member = current().getField("member");
asList(project(fields(
    computed("membershipLevel",
        member.switchOn(field -> field
            .isString(s -> s)
            .isBoolean(b -> b.cond(of("Gold"), of("Guest")))
            .<MqlString>isArray(a -> a.last())
            .defaults(d -> of("Guest"))))
)));

[ { $project: {
    membershipLevel: {
        $switch: {
          branches: [
            { case: { $eq: [ { $type: "$member" }, "string" ] }, then: "$member" },
            { case: { $eq: [ { $type: "$member" }, "bool" ] }, then: { $cond: {
                                                                           if: "$member",
                                                                           then: "Gold",
                                                                           else: "Guest" } } },
            { case: { $eq: [ { $type: "$member" }, "array" ] }, then: { $last: "$member" } }
          ],
          default: "Guest" } }
} } ]

public static MqlNumber gradeAverage(MqlArray<MqlDocument> students, String fieldName) {
    var sum = students.sum(student -> student.getInteger(fieldName));
    var avg = sum.divide(students.size());
    return avg;
}
public static MqlString evaluate(MqlNumber grade, MqlNumber cutoff1, MqlNumber cutoff2) {
    var message = grade.switchOn(on -> on
        .lte(cutoff1, g -> of("Needs improvement"))
        .lte(cutoff2, g -> of("Meets expectations"))
        .defaults(g -> of("Exceeds expectations")));
    return message;
}

var students = current().<MqlDocument>getArray("students");
asList(project(fields(
    computed("evaluation", students
        .passArrayTo(students -> gradeAverage(students, "finalGrade"))
        .passNumberTo(grade -> evaluate(grade, of(70), of(85))))
)));

[ { $project: {
    evaluation: { $switch: {
        branches: [
            { case: { $lte: [ { $avg: "$students.finalGrade" }, 70 ] },
              then: "Needs improvement"
            },
            { case: { $lte: [ { $avg: "$students.finalGrade" }, 85 ] },
              then: "Meets expectations"
            }
        ],
        default: "Exceeds expectations" } }
} } ]

var graduationYear = current().getString("graduationYear");
asList(addFields(
    new Field("reunionYear",
        graduationYear
            .parseInteger()
            .add(5))
));

[ { $addFields: {
    reunionYear: {
        $add: [ { $toInt: "$graduationYear" }, 5 ] }
} } ]

var deliveryDate = current().getString("deliveryDate");
asList(match(expr(deliveryDate
    .parseDate()
    .dayOfWeek(of("America/New_York"))
    .eq(of(2))
)));

[ { $match: {
    $expr: {
        $eq: [ {
            $dayOfWeek: {
                date: { $dateFromString: { dateString: "$deliveryDate" } },
                timezone: "America/New_York" }},
            2
        ] }
} } ]

var address = current().getDocument("mailing.address");
asList(match(expr(address
    .getString("state")
    .eq(of("WA"))
)));

[
    { $match: {
        $expr: {
            $eq: [{
                $getField: {
                    input: { $getField: { input: "$$CURRENT", field: "mailing.address"}},
                    field: "state" }},
                "WA" ]
}}}]

var warehouses = current().getMap("warehouses");
asList(project(fields(
    computed("totalInventory", warehouses
        .entries()
        .sum(v -> v.getValue()))
)));

[ { $project: {
    totalInventory: {
        $sum: {
          $getField: { $objectToArray: "$warehouses" },
        } }
} } ]

var lastName = current().getString("lastName");
var employeeID = current().getString("employeeID");
asList(project(fields(
    computed("username", lastName
        .append(employeeID)
        .toLower())
)));

[ { $project: {
    username: {
        $toLower: { $concat: ["$lastName", "$employeeID"] } }
} } ]

var rating = current().getField("rating");
asList(project(fields(
    computed("numericalRating", rating
        .isNumberOr(of(1)))
)));

[ { $project: {
    numericalRating: {
        $cond: { if: { $isNumber: "$rating" },
                 then: "$rating",
                 else: 1
        } }
} } ]