SERVER-36931 Handle returnKey option for $** indexes

1 files changed, 70 insertions, 0 deletions

diff --git a/jstests/noPassthroughWithMongod/all_paths_return_key.js b/jstests/noPassthroughWithMongod/all_paths_return_key.js
new file mode 100644
index 00000000000..75d503b320b
--- /dev/null
+++ b/jstests/noPassthroughWithMongod/all_paths_return_key.js
@@ -0,0 +1,70 @@
+/**
+ * Tests that $** indexes works with returnKey option.
+ * TODO: SERVER-36198: Move this test back to jstests/core/
+ */
+(function() {
+    'use strict';
+
+    load("jstests/aggregation/extras/utils.js");
+
+    const coll = db.all_paths_return_key;
+    coll.drop();
+
+    const assertArrayEq = (l, r) => assert(arrayEq(l, r), tojson(l) + " != " + tojson(r));
+    const assertArrayNotEq = (l, r) => assert(!arrayEq(l, r), tojson(l) + " == " + tojson(r));
+
+    // Required in order to build $** indexes.
+    assert.commandWorked(
+        db.adminCommand({setParameter: 1, internalQueryAllowAllPathsIndexes: true}));
+
+    try {
+        assert.commandWorked(coll.createIndex({"$**": 1}));
+
+        assert.commandWorked(coll.insert({a: 1, b: 2, c: {d: 2, e: 1}}));
+        assert.commandWorked(coll.insert({a: 2, b: 2, c: {d: 1, e: 2}}));
+        assert.commandWorked(coll.insert({a: 2, b: 1, c: {d: 2, e: 2}}));
+        assert.commandWorked(coll.insert({a: 1, b: 1, c: {e: 2}}));
+
+        // $** index return key with one field argument.
+        assertArrayEq(coll.find({a: 1}).returnKey().toArray(),
+                      [{"$_path": "a", a: 1}, {"$_path": "a", a: 1}]);
+
+        // $** index return key with dot path argument.
+        assertArrayEq(coll.find({"c.e": 1}).returnKey().toArray(), [{"$_path": "c.e", "c.e": 1}]);
+
+        assert.commandWorked(coll.createIndex({"a": 1}));
+
+        // $** index return key with competing regular index.
+        assertArrayEq(coll.find({a: 1}).hint({"$**": 1}).returnKey().toArray(),
+                      [{"$_path": "a", a: 1}, {"$_path": "a", a: 1}]);
+
+        assert.commandWorked(coll.createIndex({"a": 1, "b": 1}));
+
+        // $** index return key with competing compound index.
+        assertArrayNotEq(coll.find({a: 1, b: 1}).hint({"$**": 1}).returnKey().toArray(),
+                         [{a: 1, b: 1}]);
+
+        assert.commandWorked(coll.insert({a: 2, b: 2, c: {e: 2}, f: [1, 2, 3]}));
+        assert.commandWorked(coll.insert({a: 2, b: 2, c: {e: 2}, g: [{h: 1}, {i: 2}]}));
+
+        // Multikey path $** index return key.
+        assertArrayEq(coll.find({f: 1}).returnKey().toArray(), [{"$_path": "f", f: 1}]);
+
+        // Multikey subobject $** index return key.
+        assertArrayEq(coll.find({"g.h": 1}).returnKey().toArray(), [{"$_path": "g.h", "g.h": 1}]);
+
+        assert.commandWorked(coll.dropIndexes());
+        assert.commandWorked(coll.createIndex({"c.$**": 1}));
+
+        // Path specified $** index return key.
+        assertArrayEq(coll.find({"c.d": 1}).returnKey().toArray(), [{"$_path": "c.d", "c.d": 1}]);
+
+        // Path specified $** index return key with irrelevant query. We expect this query to be
+        // answered with a collection scan, in which case returnKey is expected to return empty
+        // objects.
+        assertArrayEq(coll.find({a: 1, b: 1}).returnKey().toArray(), [{}]);
+    } finally {
+        // Disable $** indexes once the tests have either completed or failed.
+        db.adminCommand({setParameter: 1, internalQueryAllowAllPathsIndexes: false});
+    }
+})();
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