// Tests that pipeline optimization works properly when the failpoint isn't triggered, and is
// disabled properly when it is triggered.
(function() {
"use strict";

load("jstests/libs/analyze_plan.js");  // For aggPlan functions.
Random.setRandomSeed();

const conn = MongoRunner.runMongod({});
assert.neq(conn, null, "Mongod failed to start up.");
const testDb = conn.getDB("test");
const coll = testDb.agg_opt;

const pops = new Set();
for (let i = 0; i < 25; ++i) {
    let pop;
    do {
        pop = Random.randInt(100000);
    } while (pops.has(pop));
    pops.add(pop);

    assert.commandWorked(coll.insert({_id: i, city: "Cleveland", pop: pop, state: "OH"}));
}

const pipeline = [{$match: {state: "OH"}}, {$sort: {pop: -1}}, {$limit: 10}];

const enabledPlan = coll.explain().aggregate(pipeline);
// Test that sort and the limit were combined.
assert.eq(aggPlanHasStage(enabledPlan, "$limit"), false);
assert.eq(aggPlanHasStage(enabledPlan, "$sort"), true);
assert.eq(enabledPlan.stages.length, 2);

const enabledResult = coll.aggregate(pipeline).toArray();

// Enable a failpoint that will cause pipeline optimizations to be skipped.
assert.commandWorked(
    testDb.adminCommand({configureFailPoint: "disablePipelineOptimization", mode: "alwaysOn"}));

const disabledPlan = coll.explain().aggregate(pipeline);
// Test that the $limit still exists and hasn't been optimized away.
assert.eq(aggPlanHasStage(disabledPlan, "$limit"), true);
assert.eq(aggPlanHasStage(disabledPlan, "$sort"), true);
assert.eq(disabledPlan.stages.length, 3);

const disabledResult = coll.aggregate(pipeline).toArray();

// Test that the result is the same with and without optimizations enabled.
assert.eq(enabledResult, disabledResult);

MongoRunner.stopMongod(conn);
}());