1 files changed, 89 insertions, 0 deletions
diff --git a/src/mongo/s/query/router_stage_remove_metadata_fields.cpp b/src/mongo/s/query/router_stage_remove_metadata_fields.cpp
new file mode 100644
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--- /dev/null
+++ b/src/mongo/s/query/router_stage_remove_metadata_fields.cpp
@@ -0,0 +1,89 @@
+/**
+ * Copyright (C) 2017 MongoDB Inc.
+ *
+ * This program is free software: you can redistribute it and/or  modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * As a special exception, the copyright holders give permission to link the
+ * code of portions of this program with the OpenSSL library under certain
+ * conditions as described in each individual source file and distribute
+ * linked combinations including the program with the OpenSSL library. You
+ * must comply with the GNU Affero General Public License in all respects
+ * for all of the code used other than as permitted herein. If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so. If you do not
+ * wish to do so, delete this exception statement from your version. If you
+ * delete this exception statement from all source files in the program,
+ * then also delete it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include <algorithm>
+
+#include "mongo/s/query/router_stage_remove_metadata_fields.h"
+
+#include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/db/pipeline/document.h"
+
+namespace mongo {
+
+RouterStageRemoveMetadataFields::RouterStageRemoveMetadataFields(
+    OperationContext* opCtx,
+    std::unique_ptr<RouterExecStage> child,
+    std::vector<StringData> metadataFields)
+    : RouterExecStage(opCtx, std::move(child)), _metaFields(std::move(metadataFields)) {
+    for (auto&& fieldName : _metaFields) {
+        invariant(fieldName[0] == '$');  // We use this information to optimize next().
+    }
+}
+
+StatusWith<ClusterQueryResult> RouterStageRemoveMetadataFields::next() {
+    auto childResult = getChildStage()->next();
+    if (!childResult.isOK() || !childResult.getValue().getResult()) {
+        return childResult;
+    }
+
+    BSONObjIterator iterator(*childResult.getValue().getResult());
+    // Find the first field that we need to remove.
+    while (iterator.more() && (*iterator).fieldName()[0] != '$' &&
+           std::find(_metaFields.begin(), _metaFields.end(), (*iterator).fieldNameStringData()) ==
+               _metaFields.end()) {
+        ++iterator;
+    }
+
+    if (!iterator.more()) {
+        // We got all the way to the end without finding any fields to remove, just return the whole
+        // document.
+        return childResult;
+    }
+
+    // Copy everything up to the first metadata field.
+    const auto firstElementBufferStart =
+        childResult.getValue().getResult()->firstElement().rawdata();
+    auto endOfNonMetaFieldBuffer = (*iterator).rawdata();
+    BSONObjBuilder builder;
+    builder.bb().appendBuf(firstElementBufferStart,
+                           endOfNonMetaFieldBuffer - firstElementBufferStart);
+
+    // Copy any remaining fields that are not metadata. We expect metadata fields are likely to be
+    // at the end of the document, so there is likely nothing else to copy.
+    while ((++iterator).more()) {
+        if (std::find(_metaFields.begin(), _metaFields.end(), (*iterator).fieldNameStringData()) ==
+            _metaFields.end()) {
+            builder.append(*iterator);
+        }
+    }
+    return {builder.obj()};
+}
+
+}  // namespace mongo