SERVER-117870 Fix aggregation view resolution concurrent to viewless timeseries upgrade (#47026)

GitOrigin-RevId: 7a9e77287614a2b91db9b6e1700761883c724f42

.github/CODEOWNERS

@@ -1198,6 +1198,9 @@ WORKSPACE.bazel @10gen/devprod-build @svc-auto-approve-bot
 # The following patterns are parsed from ./jstests/multiVersion/genericSetFCVUsage/index_builds/OWNERS.yml
 /jstests/multiVersion/genericSetFCVUsage/index_builds/**/* @10gen/server-index-builds @svc-auto-approve-bot
 
+# The following patterns are parsed from ./jstests/multiVersion/genericSetFCVUsage/query-optimization/OWNERS.yml
+/jstests/multiVersion/genericSetFCVUsage/query-optimization/**/* @10gen/query-optimization @svc-auto-approve-bot
+
 # The following patterns are parsed from ./jstests/multiVersion/genericSetFCVUsage/shard_catalog/OWNERS.yml
 /jstests/multiVersion/genericSetFCVUsage/shard_catalog/**/* @10gen/server-catalog-and-routing-shard-catalog @svc-auto-approve-bot
 

jstests/multiVersion/genericSetFCVUsage/query-optimization/BUILD.bazel

@@ -0,0 +1,12 @@
+load("//bazel:mongo_js_rules.bzl", "all_subpackage_javascript_files", "mongo_js_library")
+
+package(default_visibility = ["//visibility:public"])
+
+mongo_js_library(
+    name = "all_javascript_files",
+    srcs = glob([
+        "*.js",
+    ]),
+)
+
+all_subpackage_javascript_files()

jstests/multiVersion/genericSetFCVUsage/query-optimization/OWNERS.yml

@@ -0,0 +1,5 @@
+version: 1.0.0
+filters:
+  - "*":
+    approvers:
+      - 10gen/query-optimization

jstests/multiVersion/genericSetFCVUsage/query-optimization/viewless_timeseries_upgrade_while_resolving_view.js

@@ -0,0 +1,61 @@
+/**
+ * Tests that aggregations return correct results when a timeseries collection is upgraded from
+ * viewful to viewless format mid-query. In particular, if the aggregation resolves the timeseries
+ * view but the buckets collection is transformed to viewless timeseries before it can be acquired.
+ *
+ * @tags: [
+ *   requires_timeseries,
+ *   featureFlagCreateViewlessTimeseriesCollections,
+ * ]
+ */
+
+import {configureFailPoint} from "jstests/libs/fail_point_util.js";
+import {Thread} from "jstests/libs/parallelTester.js";
+import {ReplSetTest} from "jstests/libs/replsettest.js";
+
+// TODO(SERVER-114573): Remove this test once 9.0 becomes lastLTS.
+if (lastLTSFCV != "8.0") {
+    quit();
+}
+
+const rst = new ReplSetTest({nodes: 1});
+rst.startSet();
+rst.initiate();
+
+const primary = rst.getPrimary();
+const dbName = jsTestName();
+const collName = jsTestName();
+const testDB = primary.getDB(dbName);
+const coll = testDB[collName];
+
+// Create timeseries in viewful format.
+assert.commandWorked(testDB.adminCommand({setFeatureCompatibilityVersion: lastLTSFCV, confirm: true}));
+assert.commandWorked(testDB.createCollection(collName, {timeseries: {timeField: "t"}}));
+assert.commandWorked(coll.insertOne({t: ISODate()}));
+
+// Pause aggregation after resolving the view but before acquiring buckets.
+const fp = configureFailPoint(primary, "hangAfterAcquiringCollectionCatalog", {collection: collName});
+
+const aggThread = new Thread(
+    function (host, dbName, collName) {
+        const conn = new Mongo(host);
+        const result = conn.getDB(dbName).runCommand({aggregate: collName, pipeline: [], cursor: {}});
+        assert.commandWorked(result);
+        assert.eq(1, result.cursor.firstBatch.length);
+    },
+    primary.host,
+    dbName,
+    collName,
+);
+
+aggThread.start();
+fp.wait();
+
+// Upgrade FCV while aggregation is paused - converts viewful to viewless.
+assert.commandWorked(testDB.adminCommand({setFeatureCompatibilityVersion: latestFCV, confirm: true}));
+
+// Release aggregation. We expect non-empty results.
+fp.off();
+aggThread.join();
+
+rst.stopSet();

src/mongo/db/commands/query_cmd/aggregation_execution_state.cpp

@@ -242,6 +242,30 @@ private:
             [&](const BSONObj& data) {
                 return _aggExState.getExecutionNss().coll() == data["collection"].valueStringData();
             });
+
+        // TODO SERVER-111172: Remove this test once view-ful timeseries are removed and 9.0 is LTS.
+        if (_aggExState.isView() && !_mainAcq->collectionExists() &&
+            executionNss.isTimeseriesBucketsCollection()) {
+            // We resolved a timeseries view, but didn't later find the targeted buckets collection.
+            // If we continue execution, we will return no documents.
+            //
+            // This can happen in multiple ways, such as:
+            // 1. Because the timeseries collection is being converted to viewless timeseries.
+            // 2. Due to the timeseries collection (buckets + view) being concurrently dropped.
+            // 3. Due to a 'orphaned' timeseries view (e.g. because of a stepdown during a drop).
+            //
+            // In scenario (1), it is incorrect to return empty results. Throw CollectionBecameView
+            // to re-resolve the aggregation over the now viewless timeseries collection.
+            //
+            // In scenarios like (2) or (3), preserve the existing (v8.0) behavior of returning
+            // empty results on queries over dropped or incomplete viewful timeseries collections.
+            auto originalNssColl = CollectionCatalog::get(opCtx)->establishConsistentCollection(
+                opCtx, _aggExState.getOriginalNss(), boost::none /* readTimestamp */);
+            if (originalNssColl && originalNssColl->isTimeseriesCollection()) {
+                uasserted(ErrorCodes::CollectionBecameView,
+                          "Timeseries collection upgraded to viewless format while resolving view");
+            }
+        }
     }