SERVER-87729 Disable FCV-gating for featureFlagQueryStats (#23609)

GitOrigin-RevId: b6875f604f34732acd4f741d04d88540a83aaeca

Author: awagenmaker

jstests/multiVersion/genericBinVersion/query_stats_key_hash_version_consistency.js

@@ -8,9 +8,10 @@
 load("jstests/multiVersion/libs/multi_rs.js");
 load("jstests/libs/query_stats_utils.js");  // For getQueryStatsFindCmd and getQueryStatsKeyHashes.
 
-// TODO SERVER-87729 Start from the previous version.
-const rst = new ReplSetTest(
-    {nodes: {n1: {binVersion: "latest"}, n2: {binVersion: "latest"}, n3: {binVersion: "latest"}}});
+const rst = new ReplSetTest({
+    nodes:
+        {n1: {binVersion: "last-lts"}, n2: {binVersion: "last-lts"}, n3: {binVersion: "last-lts"}}
+});
 
 // Turn on the collecting of query stats metrics.
 rst.startSet({setParameter: {internalQueryStatsRateLimit: -1}});

jstests/noPassthrough/queryStats/query_stats_disable_after_initial_request.js

@@ -47,13 +47,8 @@ function setQueryStatsCacheSize(size) {
     assert.commandWorked(testDB.adminCommand({setParameter: 1, internalQueryStatsCacheSize: size}));
 }
 
-function setFCV(newFCV) {
-    assert.commandWorked(
-        testDB.adminCommand({setFeatureCompatibilityVersion: newFCV, confirm: true}));
-}
-
-// Tests the scenario of disabling QueryStats by setting internalQueryStatsCacheSize to
-// 0 and ending the command by running it to completion.
+// Tests the scenario of disabling query stats by setting internalQueryStatsCacheSize to 0 and
+// ending the command by running it to completion.
 testStatsAreNotCollectedWhenDisabledBeforeCommandCompletion({
     conn: testDB,
     coll,
@@ -73,26 +68,5 @@ testStatsAreNotCollectedWhenDisabledBeforeCommandCompletion({
     enableQueryStatsFn: () => setQueryStatsCacheSize("10MB")
 });
 
-// Tests the scenario of disabling query stats by downgrading the FCV and ending the command by
-// running it to completion.
-testStatsAreNotCollectedWhenDisabledBeforeCommandCompletion({
-    conn: testDB,
-    coll,
-    disableQueryStatsFn: () => setFCV(lastLTSFCV),
-    endCommandFn: (cursor) => cursor.itcount(),
-    enableQueryStatsFn: () => setFCV(binVersionToFCV("latest"))
-});
-
-// Tests the scenario of disabling query stats by downgrading the FCV and ending the command by
-// killing the cursor.
-testStatsAreNotCollectedWhenDisabledBeforeCommandCompletion({
-    conn: testDB,
-    coll,
-    disableQueryStatsFn: () => setFCV(lastLTSFCV),
-    endCommandFn: (cursor) => assert.commandWorked(
-        testDB.runCommand({killCursors: coll.getName(), cursors: [cursor.getId()]})),
-    enableQueryStatsFn: () => setFCV(binVersionToFCV("latest"))
-});
-
 MongoRunner.stopMongod(conn);
 }());

jstests/noPassthrough/queryStats/query_stats_upgrade.js

@@ -1,6 +1,11 @@
 /**
- * Test that query stats doesn't work on a lower FCV version but works after an FCV upgrade.
- * @tags: [requires_fcv_70, requires_persistence]
+ * Test that query stats works both before and after an FCV upgrade.
+ * @tags: [
+ *   # Query Stats should not skip FCV gating before 7.0.
+ *   requires_fcv_70,
+ *   # Re-uses FCV state in the dbpath.
+ *   requires_persistence
+ *  ]
  */
 load('jstests/libs/analyze_plan.js');
 load("jstests/libs/feature_flag_util.js");
@@ -23,20 +28,20 @@ function testLower(restart = false) {
         adminDB = conn.getDB("admin");
     }
 
-    assert.commandFailedWithCode(
-        testDB.adminCommand({aggregate: 1, pipeline: [{$queryStats: {}}], cursor: {}}),
-        [6579000, ErrorCodes.QueryFeatureNotAllowed]);
+    // We should be able to run a query stats pipeline even though the FCV is not upgraded.
+    assert.commandWorked(
+        testDB.adminCommand({aggregate: 1, pipeline: [{$queryStats: {}}], cursor: {}}));
 
     // Upgrade FCV.
     assert.commandWorked(adminDB.runCommand(
         {setFeatureCompatibilityVersion: binVersionToFCV("latest"), confirm: true}));
 
-    // We should be able to run a query stats pipeline now that the FCV is correct.
+    // We should still be able to run a query stats pipeline on the upgraded FCV.
     assert.commandWorked(
         testDB.adminCommand({aggregate: 1, pipeline: [{$queryStats: {}}], cursor: {}}),
     );
 }
 testLower(true);
 testLower(false);
 MongoRunner.stopMongod(conn);
-})();
+})();

src/mongo/db/query/query_stats/query_stats.cpp

@@ -222,9 +222,9 @@ void updateStatistics(const QueryStatsStore::Partition& proofOfLock,
 }  // namespace
 
 bool isQueryStatsFeatureEnabled() {
-    const auto fcvSnapshot = serverGlobalParams.featureCompatibility.acquireFCVSnapshot();
-    return fcvSnapshot.isVersionInitialized() &&
-        (feature_flags::gFeatureFlagQueryStats.isEnabled(fcvSnapshot));
+    // (Ignore FCV check): Now that query stats is enabled on v6.0, we don't want to enforce FCV
+    // gating on v7.0.
+    return feature_flags::gFeatureFlagQueryStats.isEnabledAndIgnoreFCVUnsafe();
 }
 
 void registerRequest(OperationContext* opCtx,