SERVER-23473 Add collation parameter to the distinct command

1 files changed, 16 insertions, 0 deletions

diff --git a/src/mongo/db/commands/distinct.cpp b/src/mongo/db/commands/distinct.cpp
index 16ea9564a64..10fe2533043 100644
--- a/src/mongo/db/commands/distinct.cpp
+++ b/src/mongo/db/commands/distinct.cpp
@@ -63,6 +63,7 @@ namespace {
 
 const char kKeyField[] = "key";
 const char kQueryField[] = "query";
+const char kCollationField[] = "collation";
 
 }  // namespace
 
@@ -130,6 +131,21 @@ public:
             }
         }
 
+        // Extract the collation field, if it exists.
+        // TODO SERVER-23473: Pass this collation spec object down so that it can be converted into
+        // a CollatorInterface.
+        BSONObj collation;
+        if (BSONElement collationElt = cmdObj[kCollationField]) {
+            if (collationElt.type() != BSONType::Object) {
+                return Status(ErrorCodes::TypeMismatch,
+                              str::stream() << "\"" << kCollationField
+                                            << "\" had the wrong type. Expected "
+                                            << typeName(BSONType::Object) << ", found "
+                                            << typeName(collationElt.type()));
+            }
+            collation = collationElt.embeddedObject();
+        }
+
         auto executor = getExecutorDistinct(
             txn, collection, ns, query, key, isExplain, PlanExecutor::YIELD_AUTO);
         if (!executor.isOK()) {