SERVER-7175 Support for catching conflicting mods in the update driver.

1 files changed, 57 insertions, 0 deletions

diff --git a/src/mongo/db/field_ref_set.h b/src/mongo/db/field_ref_set.h
new file mode 100644
index 00000000000..c1e8b413e81
--- /dev/null
+++ b/src/mongo/db/field_ref_set.h
@@ -0,0 +1,57 @@
+/**
+ *    Copyright (C) 2013 10gen 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/>.
+ */
+
+#pragma once
+
+#include <set>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/db/field_ref.h"
+
+namespace mongo {
+
+    /**
+     * A FieldRefSet holds a set of FieldRefs's that do not conflict with one another, that is,
+     * they target different subtrees of a given document. Two fieldRef's would conflict if they
+     * are equal or one is prefix of the other.
+     */
+    class FieldRefSet {
+        MONGO_DISALLOW_COPYING(FieldRefSet);
+    public:
+        FieldRefSet();
+
+        /**
+         * Returns true if the field 'toInsert' can be added in the set without
+         * conflicts. Otwerwise returns false and fill in '*conflict' with the field 'toInsert'
+         * clashed with.
+         *
+         * There is no ownership transfer of 'toInsert'. The caller is responsible for
+         * maintaining it alive for as long as the FieldRefSet is so. By the same token
+         * 'conflict' can only be referred to while the FieldRefSet can.
+         */
+        bool insert(const FieldRef* toInsert, const FieldRef** conflict);
+
+    private:
+        struct FieldRefPtrLessThan {
+            bool operator()(const FieldRef* lhs, const FieldRef* rhs) const;
+        };
+        typedef std::set<const FieldRef*, FieldRefPtrLessThan> FieldSet;
+
+        // A set of field_ref pointers, none of which is owned here.
+        FieldSet _fieldSet;
+    };
+
+} // namespace mongo