Index: src/window.c
==================================================================
--- src/window.c
+++ src/window.c
@@ -2217,10 +2217,11 @@
   ** return rows.
   */
   if( pMWin->eType==TK_ROWS 
    && (pMWin->eStart!=TK_UNBOUNDED||pMWin->eEnd!=TK_CURRENT||!pMWin->pOrderBy)
   ){
+    VdbeModuleComment((pParse->pVdbe, "Begin RowExprStep()"));
     windowCodeRowExprStep(pParse, p, pWInfo, regGosub, addrGosub);
   }else{
     Window *pWin;
     int bCache = 0;               /* True to use CacheStep() */
 
@@ -2241,13 +2242,15 @@
       }
     }
 
     /* Otherwise, call windowCodeDefaultStep().  */
     if( bCache ){
+      VdbeModuleComment((pParse->pVdbe, "Begin CacheStep()"));
       windowCodeCacheStep(pParse, p, pWInfo, regGosub, addrGosub);
     }else{
+      VdbeModuleComment((pParse->pVdbe, "Begin DefaultStep()"));
       windowCodeDefaultStep(pParse, p, pWInfo, regGosub, addrGosub);
     }
   }
 }
 
 #endif /* SQLITE_OMIT_WINDOWFUNC */