1 files changed, 62 insertions, 0 deletions
diff --git a/jstests/core/query/count/count_hint.js b/jstests/core/query/count/count_hint.js
new file mode 100644
index 00000000000..5ba9514de87
--- /dev/null
+++ b/jstests/core/query/count/count_hint.js
@@ -0,0 +1,62 @@
+/**
+ * Tests passing hint to the count command:
+ *   - A hint should be respected even if it results in an incorrect count.
+ *   - A bad argument to the hint() method should raise an error.
+ *   - The hint() method should support both the name of the index, and the object spec of the
+ *     index.
+ *
+ * @tags: [requires_fastcount]
+ */
+(function() {
+"use strict";
+
+var coll = db.jstests_count_hint;
+coll.drop();
+
+assert.commandWorked(coll.insert({i: 1}));
+assert.commandWorked(coll.insert({i: 2}));
+
+assert.eq(2, coll.find().count());
+
+assert.commandWorked(coll.createIndex({i: 1}));
+
+assert.eq(2, coll.find().hint("i_1").count());
+assert.eq(2, coll.find().hint({i: 1}).count());
+
+assert.eq(1, coll.find({i: 1}).hint("_id_").count());
+assert.eq(1, coll.find({i: 1}).hint({_id: 1}).count());
+
+assert.eq(2, coll.find().hint("_id_").count());
+assert.eq(2, coll.find().hint({_id: 1}).count());
+
+// Create a sparse index which should have no entries.
+assert.commandWorked(coll.createIndex({x: 1}, {sparse: true}));
+
+// A hint should be respected, even if it results in the wrong answer.
+assert.eq(0, coll.find().hint("x_1").count());
+assert.eq(0, coll.find().hint({x: 1}).count());
+
+assert.eq(0, coll.find({i: 1}).hint("x_1").count());
+assert.eq(0, coll.find({i: 1}).hint({x: 1}).count());
+
+// SERVER-14792: bad hints should cause the count to fail, even if there is no query predicate.
+assert.throws(function() {
+    coll.find().hint({bad: 1, hint: 1}).count();
+});
+assert.throws(function() {
+    coll.find({i: 1}).hint({bad: 1, hint: 1}).count();
+});
+
+assert.throws(function() {
+    coll.find().hint("BAD HINT").count();
+});
+assert.throws(function() {
+    coll.find({i: 1}).hint("BAD HINT").count();
+});
+
+// Test that a bad hint fails with the correct error code.
+let cmdRes = db.runCommand({count: coll.getName(), hint: {bad: 1, hint: 1}});
+assert.commandFailedWithCode(cmdRes, ErrorCodes.BadValue, tojson(cmdRes));
+var regex = new RegExp("hint provided does not correspond to an existing index");
+assert(regex.test(cmdRes.errmsg));
+})();