1 files changed, 24 insertions, 18 deletions

diff --git a/src/resolve.c b/src/resolve.c
index be6430deb..48d8fcb9b 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -901,6 +901,7 @@ static int resolveExprStep(Walker *pWalker, Expr *pExpr){
 #ifndef SQLITE_OMIT_WINDOWFUNC
         if( pWin ){
           Select *pSel = pNC->pWinSelect;
+          assert( pWin==pExpr->y.pWin );
           if( IN_RENAME_OBJECT==0 ){
             sqlite3WindowUpdate(pParse, pSel->pWinDefn, pWin, pDef);
           }
@@ -910,8 +911,12 @@ static int resolveExprStep(Walker *pWalker, Expr *pExpr){
           if( 0==pSel->pWin 
            || 0==sqlite3WindowCompare(pParse, pSel->pWin, pWin, 0)
           ){
-            pExpr->y.pWin->pNextWin = pSel->pWin;
-            pSel->pWin = pExpr->y.pWin;
+            pWin->pNextWin = pSel->pWin;
+            if( pSel->pWin ){
+              pSel->pWin->ppThis = &pWin->pNextWin;
+            }
+            pSel->pWin = pWin;
+            pWin->ppThis = &pSel->pWin;
           }
           pNC->ncFlags |= NC_HasWin;
         }else
@@ -1295,16 +1300,15 @@ int sqlite3ResolveOrderGroupBy(
 
 #ifndef SQLITE_OMIT_WINDOWFUNC
 /*
-** Walker callback for resolveRemoveWindows().
+** Walker callback for windowRemoveExprFromSelect().
 */
 static int resolveRemoveWindowsCb(Walker *pWalker, Expr *pExpr){
   if( ExprHasProperty(pExpr, EP_WinFunc) ){
-    Window **pp;
-    for(pp=&pWalker->u.pSelect->pWin; *pp; pp=&(*pp)->pNextWin){
-      if( *pp==pExpr->y.pWin ){
-        *pp = (*pp)->pNextWin;
-        break;
-      }    
+    Window *pWin = pExpr->y.pWin;
+    if( pWin->ppThis ){
+      *pWin->ppThis = pWin->pNextWin;
+      if( pWin->pNextWin ) pWin->pNextWin->ppThis = pWin->ppThis;
+      pWin->ppThis = 0;
     }
   }
   return WRC_Continue;
@@ -1314,16 +1318,18 @@ static int resolveRemoveWindowsCb(Walker *pWalker, Expr *pExpr){
 ** Remove any Window objects owned by the expression pExpr from the
 ** Select.pWin list of Select object pSelect.
 */
-static void resolveRemoveWindows(Select *pSelect, Expr *pExpr){
-  Walker sWalker;
-  memset(&sWalker, 0, sizeof(Walker));
-  sWalker.xExprCallback = resolveRemoveWindowsCb;
-  sWalker.u.pSelect = pSelect;
-  sqlite3WalkExpr(&sWalker, pExpr);
+static void windowRemoveExprFromSelect(Select *pSelect, Expr *pExpr){
+  if( pSelect->pWin ){
+    Walker sWalker;
+    memset(&sWalker, 0, sizeof(Walker));
+    sWalker.xExprCallback = resolveRemoveWindowsCb;
+    sWalker.u.pSelect = pSelect;
+    sqlite3WalkExpr(&sWalker, pExpr);
+  }
 }
 #else
-# define resolveRemoveWindows(x,y)
-#endif
+# define windowRemoveExprFromSelect(a, b)
+#endif /* SQLITE_OMIT_WINDOWFUNC */
 
 /*
 ** pOrderBy is an ORDER BY or GROUP BY clause in SELECT statement pSelect.
@@ -1394,7 +1400,7 @@ static int resolveOrderGroupBy(
         /* Since this expresion is being changed into a reference
         ** to an identical expression in the result set, remove all Window
         ** objects belonging to the expression from the Select.pWin list. */
-        resolveRemoveWindows(pSelect, pE);
+        windowRemoveExprFromSelect(pSelect, pE);
         pItem->u.x.iOrderByCol = j+1;
       }
     }