SERVER-64780 filter out resharding events that aren't related to the namespace being watched by a changeStream

3 files changed, 68 insertions, 1 deletions

diff --git a/etc/backports_required_for_multiversion_tests.yml b/etc/backports_required_for_multiversion_tests.yml
index 9fcc921e897..805b4e0ae8f 100644
--- a/etc/backports_required_for_multiversion_tests.yml
+++ b/etc/backports_required_for_multiversion_tests.yml
@@ -453,6 +453,8 @@ last-lts:
       test_file: jstests/sharding/update_with_dollar_fields.js
     - ticket: SERVER-63531
       test_file: jstests/replsets/buildindexes_false_commit_quorum.js
+    - ticket: SERVER-64780
+      test_file: jstest/sharding/resharding_change_stream_namespace_filtering.js
 
   # Tests that should only be excluded from particular suites should be listed under that suite.
   suites:
diff --git a/jstests/sharding/resharding_change_stream_namespace_filtering.js b/jstests/sharding/resharding_change_stream_namespace_filtering.js
new file mode 100644
index 00000000000..85b5fd8a33d
--- /dev/null
+++ b/jstests/sharding/resharding_change_stream_namespace_filtering.js
@@ -0,0 +1,63 @@
+/*
+ * Tests that a change stream on collection X doesn't erroneously see resharding events which occur
+ * on collection Y. Exercises the fix for SERVER-64780.
+ * @tags: [
+ *     uses_change_streams,
+ *     requires_fcv_50
+ * ]
+ */
+
+(function() {
+"use strict";
+
+load("jstests/libs/collection_drop_recreate.js");  // For assertDropAndRecreateCollection.
+load("jstests/libs/chunk_manipulation_util.js");   // For pauseMigrateAtStep, waitForMigrateStep and
+                                                   // unpauseMigrateAtStep.
+
+const st = new ShardingTest({
+    shards: 2,
+    rs: {nodes: 1, setParameter: {writePeriodicNoops: true, periodicNoopIntervalSecs: 1}},
+    other: {
+        configOptions: {setParameter: {reshardingCriticalSectionTimeoutMillis: 24 * 60 * 60 * 1000}}
+    }
+});
+
+const dbName = jsTestName();
+const reshardCollName = "coll_reshard";
+const otherCollName = "coll_other";
+
+const mongosDB = st.s.getDB(dbName);
+const mongosReshardColl = mongosDB[reshardCollName];
+
+const mongosOtherColl = mongosDB[otherCollName];
+const shardOtherColl = st.rs0.getPrimary().getDB(dbName)[otherCollName];
+
+// Open a {showMigrationEvents:true} change stream directly on the shard, monitoring events on
+// 'coll_other'.
+const shardOtherCollCsCursor =
+    shardOtherColl.aggregate([{$changeStream: {showMigrationEvents: true}}]);
+
+// Drop, recreate, and shard the 'coll_reshard' collection.
+assertDropAndRecreateCollection(mongosDB, reshardCollName);
+
+st.ensurePrimaryShard(dbName, st.rs0.name);
+st.shardColl(mongosReshardColl, {a: 1}, {a: 50});
+
+for (let i = 0; i < 100; ++i) {
+    assert.commandWorked(mongosReshardColl.insert({a: i, b: -i}));
+}
+
+// Reshard the 'coll_reshard' collection on {b: 1}.
+assert.commandWorked(
+    mongosDB.adminCommand({reshardCollection: mongosReshardColl.getFullName(), key: {b: 1}}));
+
+// Confirm that the change stream we opened on 'coll_other' only sees the sentinel 'insert' but does
+// not see the earlier 'reshardBegin' or 'reshardDoneCatchUp' events on the 'coll_reshard'
+// collection.
+assert.commandWorked(mongosOtherColl.insert({_id: "sentinel_write"}));
+
+assert.soon(() => shardOtherCollCsCursor.hasNext());
+assert.eq(shardOtherCollCsCursor.next().operationType, "insert");
+
+st.stop();
+})();
diff --git a/src/mongo/db/pipeline/change_stream_filter_helpers.cpp b/src/mongo/db/pipeline/change_stream_filter_helpers.cpp
index 8ab33cce834..6792facbbd3 100644
--- a/src/mongo/db/pipeline/change_stream_filter_helpers.cpp
+++ b/src/mongo/db/pipeline/change_stream_filter_helpers.cpp
@@ -236,9 +236,11 @@ std::unique_ptr<MatchExpression> buildInternalOpFilter(
     }
     internalOpTypeOrBuilder.done();
 
+    auto nsRegex = DocumentSourceChangeStream::getNsRegexForChangeStream(expCtx->ns);
     return MatchExpressionParser::parseAndNormalize(BSON("op"
                                                          << "n"
-                                                         << "$or" << internalOpTypeOrBuilder.arr()),
+                                                         << "ns" << BSONRegEx(nsRegex) << "$or"
+                                                         << internalOpTypeOrBuilder.arr()),
                                                     expCtx);
 }