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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.
*/
(function() {
"use strict";
// For arrayEq.
load("jstests/aggregation/extras/utils.js");
const collName = jsTest.name();
const coll = db.getCollection(collName);
coll.drop();
const nDocs = 10;
for (let i = 0; i < nDocs; i++) {
assert.commandWorked(coll.insert({"_id": i, "2i": i * 2, "3i": i * 3}));
}
// 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 projectPipe = [{
$project: {
"2i": 1,
"3i": 1,
"6i^2": {"$multiply": ["$2i", "$3i"]},
// _id is implicitly included.
}
}];
let correct = coll.aggregate(projectPipe).toArray();
// Then compute the same results using $addFields.
let addFieldsPipe = [{
$addFields: {
"6i^2": {"$multiply": ["$2i", "$3i"]},
// All other fields are implicitly included.
}
}];
let addFieldsResult = coll.aggregate(addFieldsPipe).toArray();
// Then assert they are the same.
assert(arrayEq(addFieldsResult, correct),
"$addFields does not work the same as a $project with computed and included fields");
// $addFields with an empty spec is allowed and should be treated as a no-op
let addFieldsEmptySpecPipe = [{$addFields: {}}];
assert(arrayEq(coll.aggregate(addFieldsEmptySpecPipe).toArray(), coll.aggregate().toArray()),
"$addFields with empty spec did not result in no-op");
})();
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