1 files changed, 44 insertions, 0 deletions
diff --git a/jstests/core/query/explain/explain5.js b/jstests/core/query/explain/explain5.js
new file mode 100644
index 00000000000..534aaf9665b
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+++ b/jstests/core/query/explain/explain5.js
@@ -0,0 +1,44 @@
+// 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
+// ]
+
+(function() {
+'use strict';
+
+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');
+})();