SERVER-30046 Support $expr constant expression in ComparisonMatchExpression

1 files changed, 18 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/variables.h b/src/mongo/db/pipeline/variables.h
index efbf115269f..4e487e811f4 100644
--- a/src/mongo/db/pipeline/variables.h
+++ b/src/mongo/db/pipeline/variables.h
@@ -64,6 +64,10 @@ public:
     static void uassertValidNameForUserWrite(StringData varName);
     static void uassertValidNameForUserRead(StringData varName);
 
+    static bool isUserDefinedVariable(Variables::Id id) {
+        return id >= 0;
+    }
+
     // Ids for builtin variables.
     static constexpr Variables::Id kRootId = Id(-1);
     static constexpr Variables::Id kRemoveId = Id(-2);
@@ -84,6 +88,20 @@ public:
     Value getValue(Variables::Id id, const Document& root) const;
 
     /**
+     * Gets the value of a user-defined variable. Should only be called when we know 'id' represents
+     * a user-defined variable.
+     */
+    Value getUserDefinedValue(Variables::Id id) const;
+
+    /**
+     * Returns whether a value for 'id' has been stored in this Variables instance.
+     */
+    bool hasUserDefinedValue(Variables::Id id) const {
+        invariant(isUserDefinedVariable(id));
+        return _valueList.size() > static_cast<size_t>(id);
+    }
+
+    /**
      * Returns Document() for non-document values, but otherwise identical to getValue(). If the
      * 'id' provided represents the special ROOT variable, then we return 'root'.
      */