SERVER-14723 fix crash in plan enumerator affecting some geo near queries

(cherry picked from commit 965cbef869f8b864caaf3bf7705f8bd82c2b81ba)

3 files changed, 29 insertions, 5 deletions

diff --git a/src/mongo/db/query/plan_enumerator.cpp b/src/mongo/db/query/plan_enumerator.cpp
index 8ffc11c0ce0..ec8c8dac4a0 100644
--- a/src/mongo/db/query/plan_enumerator.cpp
+++ b/src/mongo/db/query/plan_enumerator.cpp
@@ -408,9 +408,8 @@ namespace mongo {
             if (NULL != mandatoryPred) {
                 // We must have at least one index which can be used to answer 'mandatoryPred'.
                 invariant(!mandatoryIndices.empty());
-                enumerateMandatoryIndex(idxToFirst, idxToNotFirst, mandatoryPred,
-                                        mandatoryIndices, andAssignment);
-                return true;
+                return enumerateMandatoryIndex(idxToFirst, idxToNotFirst, mandatoryPred,
+                                               mandatoryIndices, andAssignment);
             }
 
             enumerateOneIndex(idxToFirst, idxToNotFirst, subnodes, andAssignment);
@@ -426,7 +425,7 @@ namespace mongo {
         return false;
     }
 
-    void PlanEnumerator::enumerateMandatoryIndex(const IndexToPredMap& idxToFirst,
+    bool PlanEnumerator::enumerateMandatoryIndex(const IndexToPredMap& idxToFirst,
                                                  const IndexToPredMap& idxToNotFirst,
                                                  MatchExpression* mandatoryPred,
                                                  const set<IndexID>& mandatoryIndices,
@@ -453,6 +452,13 @@ namespace mongo {
             indexAssign.index = *indexIt;
 
             IndexToPredMap::const_iterator it = idxToFirst.find(*indexIt);
+            if (idxToFirst.end() == it) {
+                // We don't have any predicate to assign to the leading field of this index.
+                // This means that we cannot generate a solution using this index, so we
+                // just move on to the next index.
+                continue;
+            }
+
             const vector<MatchExpression*>& predsOverLeadingField = it->second;
 
             if (thisIndex.multikey) {
@@ -540,6 +546,8 @@ namespace mongo {
             state.assignments.push_back(indexAssign);
             andAssignment->choices.push_back(state);
         }
+
+        return andAssignment->choices.size() > 0;
     }
 
     void PlanEnumerator::enumerateOneIndex(const IndexToPredMap& idxToFirst,
diff --git a/src/mongo/db/query/plan_enumerator.h b/src/mongo/db/query/plan_enumerator.h
index 8cccbab61c8..bd3f9c0a534 100644
--- a/src/mongo/db/query/plan_enumerator.h
+++ b/src/mongo/db/query/plan_enumerator.h
@@ -388,8 +388,11 @@ namespace mongo {
          * Generate single-index assignments for queries which contain mandatory
          * predicates (TEXT and GEO_NEAR, which are required to use a compatible index).
          * Outputs these assignments into 'andAssignment'.
+         *
+         * Returns true if it generated at least one assignment, and false if no assignment
+         * of 'mandatoryPred' is possible.
          */
-        void enumerateMandatoryIndex(const IndexToPredMap& idxToFirst,
+        bool enumerateMandatoryIndex(const IndexToPredMap& idxToFirst,
                                      const IndexToPredMap& idxToNotFirst,
                                      MatchExpression* mandatoryPred,
                                      const set<IndexID>& mandatoryIndices,
diff --git a/src/mongo/db/query/query_planner_test.cpp b/src/mongo/db/query/query_planner_test.cpp
index 808b1aba7cf..c98ea321d66 100644
--- a/src/mongo/db/query/query_planner_test.cpp
+++ b/src/mongo/db/query/query_planner_test.cpp
@@ -1908,6 +1908,19 @@ namespace {
         assertSolutionExists("{fetch: {node: {ixscan: {pattern: {x: 1, a: '2dsphere'}}}}}");
     }
 
+    // SERVER-14723
+    TEST_F(QueryPlannerTest, GeoNearMultipleRelevantIndicesButOnlyOneCompatible) {
+        addIndex(BSON("a" << "2dsphere"));
+        addIndex(BSON("b" << 1 << "a" << "2dsphere"));
+
+        runQuery(fromjson("{a: {$nearSphere: {$geometry: {type: 'Point', coordinates: [0,0]}}},"
+                          " b: {$exists: false}}"));
+
+        assertNumSolutions(1U);
+        assertSolutionExists("{fetch: {filter: {b: {$exists: false}}, node: "
+                                "{geoNear2dsphere: {a: '2dsphere'}}}}");
+    }
+
     // SERVER-3984, $or 2d index
     TEST_F(QueryPlannerTest, Or2DNonNear) {
         addIndex(BSON("a" << "2d"));