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/**
* Test that a $lookup correctly optimizes a foreign pipeline containing a $sort and a $limit. This
* test is designed to reproduce SERVER-36715.
*
* @tags: [assumes_unsharded_collection]
*/
(function() {
"use strict";
load("jstests/libs/analyze_plan.js"); // For getAggPlanStages().
const testDB = db.getSiblingDB("lookup_sort_limit");
testDB.dropDatabase();
const localColl = testDB.getCollection("local");
const fromColl = testDB.getCollection("from");
const bulk = fromColl.initializeUnorderedBulkOp();
for (let i = 0; i < 10; i++) {
bulk.insert({_id: i, foreignField: i});
}
assert.commandWorked(bulk.execute());
assert.commandWorked(localColl.insert({_id: 0}));
let res = localColl
.aggregate([{
$lookup: {
from: fromColl.getName(),
let : {},
pipeline: [{$sort: {_id: 1}}, {$limit: 1}],
as: "result"
}
}])
.toArray();
assert.eq({_id: 0, result: [{_id: 0, foreignField: 0}]}, res[0]);
// Run a similar test except with a sort that cannot be covered with an index scan.
res = localColl
.aggregate([{
$lookup: {
from: fromColl.getName(),
let : {},
pipeline: [{$sort: {foreignField: -1}}, {$limit: 1}],
as: "result"
}
}])
.toArray();
assert.eq({_id: 0, result: [{_id: 9, foreignField: 9}]}, res[0]);
}());
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