SERVER-18309 have {$in: [.., null, ..]} not use sparse indexes

Closes #979

Signed-off-by: Jason Rassi <rassi@10gen.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/mongo/db/query/planner_ixselect.cpp b/src/mongo/db/query/planner_ixselect.cpp
index c99743b4ca4..f883b5468be 100644
--- a/src/mongo/db/query/planner_ixselect.cpp
+++ b/src/mongo/db/query/planner_ixselect.cpp
@@ -154,6 +154,14 @@ namespace mongo {
                 }
             }
 
+            // Can't check for $in w/ null element w/a sparse index.
+            if (exprtype == MatchExpression::MATCH_IN && index.sparse) {
+                const InMatchExpression* expr = static_cast<const InMatchExpression*>(node);
+                if (expr->getData().hasNull()) {
+                    return false;
+                }
+            }
+
             // We can't use a btree-indexed field for geo expressions.
             if (exprtype == MatchExpression::GEO || exprtype == MatchExpression::GEO_NEAR) {
                 return false;