SERVER-15696 don't drop filters while creating a SORT_MERGE plan

2 files changed, 25 insertions, 0 deletions

diff --git a/src/mongo/db/query/planner_analysis.cpp b/src/mongo/db/query/planner_analysis.cpp
index 52b081f9ad5..a1ba92b8c70 100644
--- a/src/mongo/db/query/planner_analysis.cpp
+++ b/src/mongo/db/query/planner_analysis.cpp
@@ -203,6 +203,11 @@ namespace mongo {
                 child->addKeyMetadata = isn->addKeyMetadata;
                 child->indexIsMultiKey = isn->indexIsMultiKey;
 
+                // Copy the filter, if there is one.
+                if (isn->filter.get()) {
+                    child->filter.reset(isn->filter->shallowClone());
+                }
+
                 // Create child bounds.
                 child->bounds.fields.resize(isn->bounds.fields.size());
                 for (size_t j = 0; j < fieldsToExplode; ++j) {
diff --git a/src/mongo/db/query/query_planner_test.cpp b/src/mongo/db/query/query_planner_test.cpp
index 8467a5a70ff..1762bd49375 100644
--- a/src/mongo/db/query/query_planner_test.cpp
+++ b/src/mongo/db/query/query_planner_test.cpp
@@ -2682,6 +2682,26 @@ namespace {
                                     "{fetch: {node: {ixscan: {pattern: {d: 1, e: 1}}}}}]}}}}");
     }
 
+    // SERVER-15696: Make sure explodeForSort copies filters on IXSCAN stages to all of the
+    // scans resulting from the explode. Regex is the easiest way to have the planner create
+    // an index scan which filters using the index key.
+    TEST_F(QueryPlannerTest, ExplodeIxscanWithFilter) {
+        addIndex(BSON("a" << 1 << "b" << 1));
+
+        runQuerySortProj(fromjson("{$and: [{b: {$regex: 'foo', $options: 'i'}},"
+                                          "{a: {$in: [1, 2]}}]}"),
+                         BSON("b" << 1), BSONObj());
+
+        assertNumSolutions(2U);
+        assertSolutionExists("{sort: {pattern: {b: 1}, limit: 0, node: {cscan: {dir: 1}}}}");
+        assertSolutionExists("{fetch: {node: {mergeSort: {nodes: "
+                                "[{ixscan: {pattern: {a:1, b:1},"
+                                           "filter: {b: {$regex: 'foo', $options: 'i'}}}},"
+                                 "{ixscan: {pattern: {a:1, b:1},"
+                                           "filter: {b: {$regex: 'foo', $options: 'i'}}}}]}}}}");
+
+    }
+
     TEST_F(QueryPlannerTest, InWithSortAndLimitTrailingField) {
         addIndex(BSON("a" << 1 << "b" << -1 << "c" << 1));
         runQuerySortProjSkipLimit(fromjson("{a: {$in: [1, 2]}, b: {$gte: 0}}"),