SERVER-15279 disable hash-based index intersection by default

1 files changed, 31 insertions, 0 deletions

diff --git a/src/mongo/db/query/query_planner_test.cpp b/src/mongo/db/query/query_planner_test.cpp
index d6164250285..b329c0378b7 100644
--- a/src/mongo/db/query/query_planner_test.cpp
+++ b/src/mongo/db/query/query_planner_test.cpp
@@ -53,6 +53,7 @@ namespace {
     class QueryPlannerTest : public mongo::unittest::Test {
     protected:
         void setUp() {
+            internalQueryPlannerEnableHashIntersection = true;
             params.options = QueryPlannerParams::INCLUDE_COLLSCAN;
             addIndex(BSON("_id" << 1));
         }
@@ -4411,6 +4412,36 @@ namespace {
         assertNumSolutions(internalQueryEnumerationMaxOrSolutions);
     }
 
+    // Ensure that disabling AND_HASH intersection works properly.
+    TEST_F(QueryPlannerTest, IntersectDisableAndHash) {
+        bool oldEnableHashIntersection = internalQueryPlannerEnableHashIntersection;
+
+        // Turn index intersection on but disable hash-based intersection.
+        internalQueryPlannerEnableHashIntersection = false;
+        params.options = QueryPlannerParams::NO_TABLE_SCAN | QueryPlannerParams::INDEX_INTERSECTION;
+
+        addIndex(BSON("a" << 1));
+        addIndex(BSON("b" << 1));
+        addIndex(BSON("c" << 1));
+
+        runQuery(fromjson("{a: {$gt: 1}, b: 1, c: 1}"));
+
+        // We should do an AND_SORT intersection of {b: 1} and {c: 1}, but no AND_HASH plans.
+        assertNumSolutions(4U);
+        assertSolutionExists("{fetch: {filter: {b: 1, c: 1}, node: {ixscan: "
+                                "{pattern: {a: 1}, bounds: {a: [[1,Infinity,false,true]]}}}}}");
+        assertSolutionExists("{fetch: {filter: {a:{$gt:1},c:1}, node: {ixscan: "
+                                "{pattern: {b: 1}, bounds: {b: [[1,1,true,true]]}}}}}");
+        assertSolutionExists("{fetch: {filter: {a:{$gt:1},b:1}, node: {ixscan: "
+                                "{pattern: {c: 1}, bounds: {c: [[1,1,true,true]]}}}}}");
+        assertSolutionExists("{fetch: {filter: {a:{$gt:1}}, node: {andSorted: {nodes: ["
+                                    "{ixscan: {filter: null, pattern: {b:1}}},"
+                                    "{ixscan: {filter: null, pattern: {c:1}}}]}}}}");
+
+        // Restore the old value of the has intersection switch.
+        internalQueryPlannerEnableHashIntersection = oldEnableHashIntersection;
+    }
+
     //
     // Index intersection cases for SERVER-12825: make sure that
     // we don't generate an ixisect plan if a compound index is