SERVER-38372 Fix rollback of index drop to update CollectionInfoCache.

1 files changed, 35 insertions, 0 deletions

diff --git a/jstests/core/rollback_index_drop.js b/jstests/core/rollback_index_drop.js
new file mode 100644
index 00000000000..3e7c3a97952
--- /dev/null
+++ b/jstests/core/rollback_index_drop.js
@@ -0,0 +1,35 @@
+// Test that when an index drop rolls back, the index remains valid, and the server continues to
+// correctly maintain the index's set of keys.
+//
+// This test was designed to reproduce SERVER-38372.
+//
+// @tags: [does_not_support_stepdowns, assumes_unsharded_collection]
+(function() {
+    "use strict";
+
+    const coll = db.rollback_index_drop;
+    coll.drop();
+
+    assert.commandWorked(coll.insert([{a: 1}, {a: 2}, {a: 3}]));
+    assert.commandWorked(coll.createIndex({a: 1}));
+
+    // Verify that the index has the expected set of keys.
+    assert.eq([{a: 1}, {a: 2}, {a: 3}],
+              coll.find().hint({a: 1}).sort({a: 1}).returnKey().toArray());
+
+    // Run a dropIndexes command that attempts to drop both {a: 1} and an invalid index. This should
+    // cause the drop of {a: 1} to rollback, since the set of index drops happen atomically.
+    assert.commandFailedWithCode(
+        db.runCommand({dropIndexes: coll.getName(), index: ["a_1", "unknown"]}),
+        ErrorCodes.IndexNotFound);
+
+    // Verify that the {a: 1} index is still present in listIndexes output.
+    const indexList = coll.getIndexes();
+    assert.neq(undefined, indexList.find((idx) => idx.name === "a_1"), indexList);
+
+    // Write to the collection and ensure that the resulting set of index keys is correct.
+    assert.commandWorked(coll.update({a: 3}, {$inc: {a: 1}}));
+    assert.commandWorked(coll.insert({a: 5}));
+    assert.eq([{a: 1}, {a: 2}, {a: 4}, {a: 5}],
+              coll.find().hint({a: 1}).sort({a: 1}).returnKey().toArray());
+}());