// Check explain results for a plan that uses an index to obtain the requested sort order.
// @tags: [
//   assumes_balancer_off,
//   assumes_read_concern_local,
//   operations_longer_than_stepdown_interval,  # large bulk inserts
// ]

const t = db.jstests_explain5;
t.drop();

assert.commandWorked(t.createIndexes([{a: 1}, {b: 1}]));

let docs = [];
for (let i = 0; i < 1000; ++i) {
    docs.push({_id: i, a: i, b: i % 3});
}
assert.commandWorked(t.insert(docs));

// Query with an initial set of documents.
const explain1 = t
    .find({a: {$gte: 0}, b: 2})
    .sort({a: 1})
    .hint({a: 1})
    .explain("executionStats");
jsTestLog("explain5 explain output after initial documents: " + tojson(explain1));
const stats1 = explain1.executionStats;
assert.eq(333, stats1.nReturned, "wrong nReturned for explain1");
assert.eq(1000, stats1.totalKeysExamined, "wrong totalKeysExamined for explain1");

docs = [];
for (let i = 1000; i < 2000; ++i) {
    docs.push({_id: i, a: i, b: i % 3});
}
assert.commandWorked(t.insert(docs));

// Query with some additional documents.
const explain2 = t
    .find({a: {$gte: 0}, b: 2})
    .sort({a: 1})
    .hint({a: 1})
    .explain("executionStats");
jsTestLog("explain5 explain output after additional documents: " + tojson(explain2));
const stats2 = explain2.executionStats;
assert.eq(666, stats2.nReturned, "wrong nReturned for explain2");
assert.eq(2000, stats2.totalKeysExamined, "wrong totalKeysExamined for explain2");