SERVER-35921 Make IXSCAN use the proper MinKey/MaxKey bounds on LT and GT

(cherry picked from commit b1285a2acb60cbf7c268cb5499fbf5d674d490b2)
(cherry picked from commit b315dcfc8145c6b898b21916bef4bec18e95ac54)

6 files changed, 28 insertions, 15 deletions

diff --git a/jstests/core/index_bounds_maxkey.js b/jstests/core/index_bounds_maxkey.js
index b22af082b13..ab152230904 100644
--- a/jstests/core/index_bounds_maxkey.js
+++ b/jstests/core/index_bounds_maxkey.js
@@ -18,7 +18,7 @@
     assertCoveredQueryAndCount(
         {collection: coll, query: {a: {$gte: MaxKey}}, project: proj, count: 1});
     assertCoveredQueryAndCount(
-        {collection: coll, query: {a: {$lt: MaxKey}}, project: proj, count: 1});
+        {collection: coll, query: {a: {$lt: MaxKey}}, project: proj, count: 0});
     assertCoveredQueryAndCount(
         {collection: coll, query: {a: {$lte: MaxKey}}, project: proj, count: 1});
 
diff --git a/jstests/core/index_bounds_minkey.js b/jstests/core/index_bounds_minkey.js
index 6fa9d4f0d1e..25fc4f56fc7 100644
--- a/jstests/core/index_bounds_minkey.js
+++ b/jstests/core/index_bounds_minkey.js
@@ -14,7 +14,7 @@
     // Test that queries involving comparison operators with MinKey are covered.
     const proj = {a: 1, _id: 0};
     assertCoveredQueryAndCount(
-        {collection: coll, query: {a: {$gt: MinKey}}, project: proj, count: 1});
+        {collection: coll, query: {a: {$gt: MinKey}}, project: proj, count: 0});
     assertCoveredQueryAndCount(
         {collection: coll, query: {a: {$gte: MinKey}}, project: proj, count: 1});
     assertCoveredQueryAndCount(
diff --git a/jstests/core/min_max_key.js b/jstests/core/min_max_key.js
index d65d68292fa..744bdff2b49 100644
--- a/jstests/core/min_max_key.js
+++ b/jstests/core/min_max_key.js
@@ -89,9 +89,6 @@
     testTypeBracketedQueries();
 
     assert.commandWorked(coll.createIndex({a: 1}));
-    // TODO: SERVER-35921 The results of the queries above should not change based on the
-    // presence of an index
-    assert.commandWorked(coll.dropIndexes());
 
     testQueriesWithMinOrMaxKey();
     testTypeBracketedQueries();
diff --git a/src/mongo/db/query/index_bounds_builder.cpp b/src/mongo/db/query/index_bounds_builder.cpp
index 503ee1f8b9d..48ee291b288 100644
--- a/src/mongo/db/query/index_bounds_builder.cpp
+++ b/src/mongo/db/query/index_bounds_builder.cpp
@@ -250,6 +250,13 @@ void IndexBoundsBuilder::allValuesForField(const BSONElement& elt, OrderedInterv
         makeRangeInterval(bob.obj(), BoundInclusion::kIncludeBothStartAndEndKeys));
 }
 
+Interval IndexBoundsBuilder::allValuesRespectingInclusion(BoundInclusion bi) {
+    BSONObjBuilder bob;
+    bob.appendMinKey("");
+    bob.appendMaxKey("");
+    return makeRangeInterval(bob.obj(), bi);
+}
+
 Interval IndexBoundsBuilder::allValues() {
     BSONObjBuilder bob;
     bob.appendMinKey("");
@@ -479,9 +486,10 @@ void IndexBoundsBuilder::translate(const MatchExpression* expr,
         const LTMatchExpression* node = static_cast<const LTMatchExpression*>(expr);
         BSONElement dataElt = node->getData();
 
-        // Everything is <= MaxKey.
+        // Everything is < MaxKey, except for MaxKey.
         if (MaxKey == dataElt.type()) {
-            oilOut->intervals.push_back(allValues());
+            oilOut->intervals.push_back(allValuesRespectingInclusion(
+                IndexBounds::makeBoundInclusionFromBoundBools(true, false)));
             *tightnessOut =
                 index.collator ? IndexBoundsBuilder::INEXACT_FETCH : IndexBoundsBuilder::EXACT;
             return;
@@ -517,9 +525,10 @@ void IndexBoundsBuilder::translate(const MatchExpression* expr,
         const GTMatchExpression* node = static_cast<const GTMatchExpression*>(expr);
         BSONElement dataElt = node->getData();
 
-        // Everything is > MinKey.
+        // Everything is > MinKey, except MinKey.
         if (MinKey == dataElt.type()) {
-            oilOut->intervals.push_back(allValues());
+            oilOut->intervals.push_back(allValuesRespectingInclusion(
+                IndexBounds::makeBoundInclusionFromBoundBools(false, true)));
             *tightnessOut =
                 index.collator ? IndexBoundsBuilder::INEXACT_FETCH : IndexBoundsBuilder::EXACT;
             return;
diff --git a/src/mongo/db/query/index_bounds_builder.h b/src/mongo/db/query/index_bounds_builder.h
index 52e33853b8b..9f396bd144e 100644
--- a/src/mongo/db/query/index_bounds_builder.h
+++ b/src/mongo/db/query/index_bounds_builder.h
@@ -166,6 +166,11 @@ public:
      */
     static Interval allValues();
 
+    /**
+     * Returns an Interval from minKey to maxKey, preserving the specified inclusion.
+     */
+    static Interval allValuesRespectingInclusion(BoundInclusion bi);
+
     static void translateRegex(const RegexMatchExpression* rme,
                                const IndexEntry& index,
                                OrderedIntervalList* oil,
diff --git a/src/mongo/db/query/index_bounds_builder_test.cpp b/src/mongo/db/query/index_bounds_builder_test.cpp
index 392204f548c..75062d44c4f 100644
--- a/src/mongo/db/query/index_bounds_builder_test.cpp
+++ b/src/mongo/db/query/index_bounds_builder_test.cpp
@@ -439,9 +439,9 @@ TEST(IndexBoundsBuilderTest, TranslateLtMaxKey) {
     IndexBoundsBuilder::translate(expr.get(), elt, testIndex, &oil, &tightness);
     ASSERT_EQUALS(oil.name, "a");
     ASSERT_EQUALS(oil.intervals.size(), 1U);
-    ASSERT_EQUALS(oil.intervals[0].toString(), "[MinKey, MaxKey]");
+    ASSERT_EQUALS(oil.intervals[0].toString(), "[MinKey, MaxKey)");
     ASSERT_TRUE(oil.intervals[0].startInclusive);
-    ASSERT_TRUE(oil.intervals[0].endInclusive);
+    ASSERT_FALSE(oil.intervals[0].endInclusive);
     ASSERT_EQUALS(tightness, IndexBoundsBuilder::EXACT);
 }
 
@@ -583,8 +583,8 @@ TEST(IndexBoundsBuilderTest, TranslateGtMinKey) {
     IndexBoundsBuilder::translate(expr.get(), elt, testIndex, &oil, &tightness);
     ASSERT_EQUALS(oil.name, "a");
     ASSERT_EQUALS(oil.intervals.size(), 1U);
-    ASSERT_EQUALS(oil.intervals[0].toString(), "[MinKey, MaxKey]");
-    ASSERT_TRUE(oil.intervals[0].startInclusive);
+    ASSERT_EQUALS(oil.intervals[0].toString(), "(MinKey, MaxKey]");
+    ASSERT_FALSE(oil.intervals[0].startInclusive);
     ASSERT_TRUE(oil.intervals[0].endInclusive);
     ASSERT_EQUALS(tightness, IndexBoundsBuilder::EXACT);
 }
@@ -2485,7 +2485,8 @@ TEST(IndexBoundsBuilderTest, LTMaxKeyWithCollator) {
     ASSERT_EQUALS(oil.name, "a");
     ASSERT_EQUALS(oil.intervals.size(), 1U);
     ASSERT_EQUALS(Interval::INTERVAL_EQUALS,
-                  oil.intervals[0].compare(IndexBoundsBuilder::allValues()));
+                  oil.intervals[0].compare(IndexBoundsBuilder::allValuesRespectingInclusion(
+                      BoundInclusion::kIncludeStartKeyOnly)));
     ASSERT_EQUALS(tightness, IndexBoundsBuilder::INEXACT_FETCH);
 }
 
@@ -2525,7 +2526,8 @@ TEST(IndexBoundsBuilderTest, GTMinKeyWithCollator) {
     ASSERT_EQUALS(oil.name, "a");
     ASSERT_EQUALS(oil.intervals.size(), 1U);
     ASSERT_EQUALS(Interval::INTERVAL_EQUALS,
-                  oil.intervals[0].compare(IndexBoundsBuilder::allValues()));
+                  oil.intervals[0].compare(IndexBoundsBuilder::allValuesRespectingInclusion(
+                      BoundInclusion::kIncludeEndKeyOnly)));
     ASSERT_EQUALS(tightness, IndexBoundsBuilder::INEXACT_FETCH);
 }