SERVER-8758 - IndexSet fix for ab vs a

1 files changed, 14 insertions, 2 deletions

diff --git a/src/mongo/db/index_set.cpp b/src/mongo/db/index_set.cpp
index 4d7cb62a759..65f74ed54ea 100644
--- a/src/mongo/db/index_set.cpp
+++ b/src/mongo/db/index_set.cpp
@@ -47,16 +47,28 @@ namespace mongo {
 
             StringData idx( *i );
 
-            if ( use.startsWith( idx ) )
+            if ( _startsWith( use, idx ) )
                 return true;
 
-            if ( idx.startsWith( use ) )
+            if ( _startsWith( idx, use ) )
                 return true;
         }
 
         return false;
     }
 
+    bool IndexPathSet::_startsWith( const StringData& a, const StringData& b ) const {
+        if ( !a.startsWith( b ) )
+            return false;
+
+        // make sure there is a dot or EOL right after
+
+        if ( a.size() == b.size() )
+            return true;
+
+        return a[b.size()] == '.';
+    }
+
     bool getCanonicalIndexField( const StringData& fullName, string* out ) {
         // check if fieldName contains ".$" or ".###" substrings (#=digit) and skip them
         // however do not skip the first field even if it meets these criteria