SERVER-26033 Allow simple range to exclude start key

1 files changed, 13 insertions, 3 deletions

diff --git a/src/mongo/db/query/query_planner_common.cpp b/src/mongo/db/query/query_planner_common.cpp
index 8f129e54e5b..33eb72100cc 100644
--- a/src/mongo/db/query/query_planner_common.cpp
+++ b/src/mongo/db/query/query_planner_common.cpp
@@ -45,9 +45,19 @@ void QueryPlannerCommon::reverseScans(QuerySolutionNode* node) {
 
         if (isn->bounds.isSimpleRange) {
             std::swap(isn->bounds.startKey, isn->bounds.endKey);
-            // XXX: Not having a startKeyInclusive means that if we reverse a max/min query
-            // we have different results with and without the reverse...
-            isn->bounds.endKeyInclusive = true;
+            // If only one bound is included, swap which one is included.
+            switch (isn->bounds.boundInclusion) {
+                case BoundInclusion::kIncludeStartKeyOnly:
+                    isn->bounds.boundInclusion = BoundInclusion::kIncludeEndKeyOnly;
+                    break;
+                case BoundInclusion::kIncludeEndKeyOnly:
+                    isn->bounds.boundInclusion = BoundInclusion::kIncludeStartKeyOnly;
+                    break;
+                case BoundInclusion::kIncludeBothStartAndEndKeys:
+                case BoundInclusion::kExcludeBothStartAndEndKeys:
+                    // These are both symmetric so no change needed.
+                    break;
+            }
         } else {
             for (size_t i = 0; i < isn->bounds.fields.size(); ++i) {
                 std::vector<Interval>& iv = isn->bounds.fields[i].intervals;