SERVER-39764 fix bug where $in is planned from cache incorrectly

1 files changed, 45 insertions, 0 deletions

diff --git a/jstests/noPassthroughWithMongod/ne_array_indexability.js b/jstests/noPassthroughWithMongod/ne_array_indexability.js
new file mode 100644
index 00000000000..284389c1303
--- /dev/null
+++ b/jstests/noPassthroughWithMongod/ne_array_indexability.js
@@ -0,0 +1,45 @@
+/**
+ * Test that $ne: [] queries are cached correctly. See SERVER-39764.
+ */
+(function() {
+    const coll = db.ne_array_indexability;
+    coll.drop();
+
+    coll.createIndex({"obj": 1});
+    coll.createIndex({"obj": 1, "abc": 1});
+
+    assert.commandWorked(coll.insert({obj: "hi there"}));
+
+    function runTest(queryToCache, queryToRunAfterCaching) {
+        assert.eq(coll.find(queryToCache).itcount(), 1);
+        assert.eq(coll.find(queryToCache).itcount(), 1);
+
+        const cacheEntries =
+            coll.aggregate([
+                    {$planCacheStats: {}},
+                    {
+                      $match: {
+                          isActive: true,
+                          createdFromQuery: {query: queryToCache, sort: {}, projection: {}}
+                      }
+                    }
+                ])
+                .toArray();
+        assert.eq(cacheEntries.length, 1);
+
+        assert.eq(coll.find(queryToRunAfterCaching).itcount(), 1);
+
+        const explain = assert.commandWorked(coll.find(queryToRunAfterCaching).explain());
+        // The query with the $ne: array should have the same queryHash, but a different
+        // planCacheKey.
+        assert.eq(explain.queryPlanner.queryHash, cacheEntries[0].queryHash);
+        assert.neq(explain.queryPlanner.planCacheKey, cacheEntries[0].planCacheKey);
+    }
+
+    runTest({'obj': {$ne: 'def'}}, {'obj': {$ne: [[1]]}});
+
+    // Clear the cache.
+    assert.commandWorked(coll.runCommand('planCacheClear'));
+
+    runTest({'obj': {$nin: ['abc', 'def']}}, {'obj': {$nin: [[1], 'abc']}});
+})();