SERVER-67086 Fix gTimeseriesMetricIndexes usage

3 files changed, 20 insertions, 24 deletions

diff --git a/src/mongo/db/timeseries/timeseries_commands_conversion_helper.cpp b/src/mongo/db/timeseries/timeseries_commands_conversion_helper.cpp
index be234d0d95f..7b8899a101a 100644
--- a/src/mongo/db/timeseries/timeseries_commands_conversion_helper.cpp
+++ b/src/mongo/db/timeseries/timeseries_commands_conversion_helper.cpp
@@ -83,12 +83,12 @@ CreateIndexesCommand makeTimeseriesCreateIndexesCommand(OperationContext* opCtx,
     std::vector<mongo::BSONObj> indexes;
     for (const auto& origIndex : origIndexes) {
         BSONObjBuilder builder;
-        bool isBucketsIndexSpecCompatibleForDowngrade = true;
+        bool includeOriginalSpec = false;
         for (const auto& elem : origIndex) {
             if (elem.fieldNameStringData() == IndexDescriptor::kPartialFilterExprFieldName) {
-                if (feature_flags::gTimeseriesMetricIndexes.isEnabledAndIgnoreFCV() &&
-                    serverGlobalParams.featureCompatibility.isFCVUpgradingToOrAlreadyLatest()) {
-                    isBucketsIndexSpecCompatibleForDowngrade = false;
+                if (feature_flags::gTimeseriesMetricIndexes.isEnabled(
+                        serverGlobalParams.featureCompatibility)) {
+                    includeOriginalSpec = true;
                 } else {
                     uasserted(ErrorCodes::InvalidOptions,
                               "Partial indexes are not supported on time-series collections");
@@ -195,11 +195,11 @@ CreateIndexesCommand makeTimeseriesCreateIndexesCommand(OperationContext* opCtx,
                                       << " Command request: " << redact(origCmd.toBSON({})),
                         bucketsIndexSpecWithStatus.isOK());
 
-                if (!timeseries::isBucketsIndexSpecCompatibleForDowngrade(
+                if (timeseries::shouldIncludeOriginalSpec(
                         options,
                         BSON(NewIndexSpec::kKeyFieldName
                              << bucketsIndexSpecWithStatus.getValue()))) {
-                    isBucketsIndexSpecCompatibleForDowngrade = false;
+                    includeOriginalSpec = true;
                 }
 
                 builder.append(NewIndexSpec::kKeyFieldName,
@@ -212,12 +212,11 @@ CreateIndexesCommand makeTimeseriesCreateIndexesCommand(OperationContext* opCtx,
             builder.append(elem);
         }
 
-        if (feature_flags::gTimeseriesMetricIndexes.isEnabledAndIgnoreFCV() &&
-            !isBucketsIndexSpecCompatibleForDowngrade) {
+        if (feature_flags::gTimeseriesMetricIndexes.isEnabled(
+                serverGlobalParams.featureCompatibility) &&
+            includeOriginalSpec) {
             // Store the original user index definition on the transformed index definition for the
-            // time-series buckets collection if this is a newly supported index type on time-series
-            // collections. This is to avoid any additional downgrade steps for index types already
-            // supported in 5.0.
+            // time-series buckets collection.
             builder.appendObject(IndexDescriptor::kOriginalSpecFieldName, origIndex.objdata());
         }
 
diff --git a/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.cpp b/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.cpp
index 83b6e3f6e9d..4dcf9a73eda 100644
--- a/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.cpp
+++ b/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.cpp
@@ -149,7 +149,8 @@ StatusWith<BSONObj> createBucketsSpecFromTimeseriesSpec(const TimeseriesOptions&
 
         // Indexes on measurement fields are only supported when the 'gTimeseriesMetricIndexes'
         // feature flag is enabled.
-        if (!feature_flags::gTimeseriesMetricIndexes.isEnabledAndIgnoreFCV()) {
+        if (!feature_flags::gTimeseriesMetricIndexes.isEnabled(
+                serverGlobalParams.featureCompatibility)) {
             auto reason = str::stream();
             reason << "Invalid index spec for time-series collection: "
                    << redact(timeseriesIndexSpecBSON) << ". ";
@@ -366,7 +367,7 @@ StatusWith<BSONObj> createBucketsShardKeySpecFromTimeseriesShardKeySpec(
 boost::optional<BSONObj> createTimeseriesIndexFromBucketsIndex(
     const TimeseriesOptions& timeseriesOptions, const BSONObj& bucketsIndex) {
     bool timeseriesMetricIndexesFeatureFlagEnabled =
-        feature_flags::gTimeseriesMetricIndexes.isEnabledAndIgnoreFCV();
+        feature_flags::gTimeseriesMetricIndexes.isEnabled(serverGlobalParams.featureCompatibility);
 
     if (bucketsIndex.hasField(kOriginalSpecFieldName) &&
         timeseriesMetricIndexesFeatureFlagEnabled) {
@@ -406,21 +407,16 @@ std::list<BSONObj> createTimeseriesIndexesFromBucketsIndexes(
     return indexSpecs;
 }
 
-bool isBucketsIndexSpecCompatibleForDowngrade(const TimeseriesOptions& timeseriesOptions,
-                                              const BSONObj& bucketsIndex) {
+bool shouldIncludeOriginalSpec(const TimeseriesOptions& timeseriesOptions,
+                               const BSONObj& bucketsIndex) {
     if (!bucketsIndex.hasField(kKeyFieldName)) {
         return false;
     }
 
-    if (bucketsIndex.hasField(kPartialFilterExpressionFieldName)) {
-        // Partial indexes are not supported in FCV < 5.2.
-        return false;
-    }
-
     return createTimeseriesIndexSpecFromBucketsIndexSpec(
                timeseriesOptions,
                bucketsIndex.getField(kKeyFieldName).Obj(),
-               /*timeseriesMetricIndexesFeatureFlagEnabled=*/false) != boost::none;
+               /*timeseriesMetricIndexesFeatureFlagEnabled=*/false) == boost::none;
 }
 
 bool doesBucketsIndexIncludeMeasurement(OperationContext* opCtx,
diff --git a/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.h b/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.h
index ad1bb795fd2..144893c0d77 100644
--- a/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.h
+++ b/src/mongo/db/timeseries/timeseries_index_schema_conversion_functions.h
@@ -71,10 +71,11 @@ std::list<BSONObj> createTimeseriesIndexesFromBucketsIndexes(
     const TimeseriesOptions& timeseriesOptions, const std::list<BSONObj>& bucketsIndexes);
 
 /**
- * Returns true if the 'bucketsIndex' is compatible for FCV downgrade.
+ * Returns true if the original index specification should be included when creating an index on the
+ * time-series buckets collection.
  */
-bool isBucketsIndexSpecCompatibleForDowngrade(const TimeseriesOptions& timeseriesOptions,
-                                              const BSONObj& bucketsIndex);
+bool shouldIncludeOriginalSpec(const TimeseriesOptions& timeseriesOptions,
+                               const BSONObj& bucketsIndex);
 
 /**
  * Returns true if 'bucketsIndex' uses a measurement field, excluding the time field. Checks both