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/**
* $addFields can be used to add fixed and computed fields to documents while preserving the
* original document. Verify that using $addFields and adding computed fields in a $project yield
* the same result. Use the sample case of computing weather metadata.
* @tags: [
* sbe_incompatible,
* ]
*/
(function() {
"use strict";
// For arrayEq.
load("jstests/aggregation/extras/utils.js");
const collName = jsTest.name();
const coll = db.getCollection(collName);
coll.drop();
Random.setRandomSeed();
const nDocs = 10;
for (let i = 0; i < nDocs; i++) {
assert.commandWorked(coll.insert(generateRandomDocument()));
}
/**
* Helper to generate an array of specified length of numbers in the specified range.
*/
function randomArray(length, minValue, maxValue) {
let array = [];
for (let i = 0; i < length; i++) {
array.push((Random.rand() * (maxValue - minValue)) + minValue);
}
return array;
}
/**
* Helper to generate a randomized document with the following schema:
* {
* month: <integer month of year>,
* day: <integer day of month>,
* temperatures: <array of 24 decimal temperatures>
* }
*/
function generateRandomDocument() {
const minTemp = -40;
const maxTemp = 120;
return {
month: Random.randInt(12) + 1, // 1-12
day: Random.randInt(31) + 1, // 1-31
temperatures: randomArray(24, minTemp, maxTemp),
};
}
// Add the minimum, maximum, and average temperatures, and make sure that doing the same
// with addFields yields the correct answer.
// First compute with $project, since we know all the fields in this document.
let projectWeatherPipe = [{
$project: {
"month": 1,
"day": 1,
"temperatures": 1,
"minTemp": {"$min": "$temperatures"},
"maxTemp": {"$max": "$temperatures"},
"average": {"$avg": "$temperatures"},
// _id is implicitly included.
}
}];
let correctWeather = coll.aggregate(projectWeatherPipe).toArray();
// Then compute the same results using $addFields.
let addFieldsWeatherPipe = [{
$addFields: {
"minTemp": {"$min": "$temperatures"},
"maxTemp": {"$max": "$temperatures"},
"average": {"$avg": "$temperatures"},
// All other fields are implicitly included.
}
}];
let addFieldsResult = coll.aggregate(addFieldsWeatherPipe).toArray();
// Then assert they are the same.
assert(arrayEq(addFieldsResult, correctWeather),
"$addFields does not work the same as a $project with computed and included fields");
}());
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