SERVER-21612 Reorder lookup and match.

1 files changed, 23 insertions, 0 deletions

diff --git a/src/mongo/db/matcher/expression_algo.h b/src/mongo/db/matcher/expression_algo.h
index 0b377830274..c8747acac33 100644
--- a/src/mongo/db/matcher/expression_algo.h
+++ b/src/mongo/db/matcher/expression_algo.h
@@ -28,12 +28,17 @@
  *    it in the license file.
  */
 
+#include "mongo/stdx/functional.h"
+
 namespace mongo {
 
 class MatchExpression;
+struct DepsTracker;
 
 namespace expression {
 
+using NodeTraversalFunc = stdx::function<void(MatchExpression*, std::string)>;
+
 /**
  * Returns true if the documents matched by 'lhs' are a subset of the documents matched by
  * 'rhs', i.e. a document matched by 'lhs' must also be matched by 'rhs', and false otherwise.
@@ -75,6 +80,24 @@ bool isSplittableBy(const MatchExpression& expr, const std::set<std::string>& pa
 bool isIndependentOf(const MatchExpression& expr, const std::set<std::string>& pathSet);
 
 /**
+ * Returns whether the path represented by 'first' is an prefix of the path represented by 'second'.
+ * Equality is not considered a prefix. For example:
+ *
+ * a.b is a prefix of a.b.c
+ * a.b is not a prefix of a.balloon
+ * a is a prefix of a.b
+ * a is not a prefix of a
+ * a.b is not a prefix of a
+ */
+bool isPathPrefixOf(StringData first, StringData second);
+
+/**
+ * Applies 'func' to each node of 'expr', where the first argument is a pointer to that actual node
+ * (not a copy), and the second argument is the path to that node.
+ */
+void mapOver(MatchExpression* expr, NodeTraversalFunc func, std::string path = "");
+
+/**
  * Attempt to split 'expr' into two MatchExpressions, where the first is not reliant upon any
  * path from 'fields', such that applying the matches in sequence is equivalent to applying
  * 'expr'. Takes ownership of 'expr'.