Fixed bug mdev-9754.

Each window name has to be resolved only once.

mysql-test/r/win.result

@@ -1257,3 +1257,43 @@ a	row_number() over (partition by a order by b)
 3	1
 3	2
 drop table t1;
+# 
+#  mdev-9754: Window name resolution in prepared statement 
+# 
+create table t0 (a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (pk int, c int);
+insert into t1 select a+1,1 from t0;
+update t1 set c=2 where pk not in (1,2,3,4);
+select * from t1;
+pk	c
+1	1
+2	1
+3	1
+4	1
+5	2
+6	2
+7	2
+8	2
+9	2
+10	2
+prepare stmt from 
+'select 
+  pk, c, 
+  count(*) over w1 as CNT
+from t1
+window w1 as (partition by c order by pk 
+              rows between 2 preceding and 2 following)';
+execute stmt;
+pk	c	CNT
+1	1	3
+2	1	4
+3	1	4
+4	1	3
+5	2	3
+6	2	4
+7	2	5
+8	2	5
+9	2	4
+10	2	3
+drop table t0,t1;

mysql-test/t/win.test

@@ -785,7 +785,28 @@ execute stmt;
 
 drop table t1;
 
+--echo # 
+--echo #  mdev-9754: Window name resolution in prepared statement 
+--echo # 
 
+create table t0 (a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+ 
+create table t1 (pk int, c int);
+insert into t1 select a+1,1 from t0;
+update t1 set c=2 where pk not in (1,2,3,4);
+select * from t1;
+ 
+prepare stmt from 
+'select 
+  pk, c, 
+  count(*) over w1 as CNT
+from t1
+window w1 as (partition by c order by pk 
+              rows between 2 preceding and 2 following)';
+execute stmt;
+
+drop table t0,t1;
 
 
 

sql/item_windowfunc.cc

@@ -7,6 +7,11 @@
 bool
 Item_window_func::resolve_window_name(THD *thd)
 {
+  if (window_spec)
+  {
+    /* The window name has been already resolved */
+    return false;
+  }
   DBUG_ASSERT(window_name != NULL && window_spec == NULL);
   char *ref_name= window_name->str;
 
@@ -15,7 +20,8 @@ Item_window_func::resolve_window_name(THD *thd)
     First look for the deinition of the window with 'window_name'
     in the current select
   */
-  List<Window_spec> curr_window_specs=thd->lex->current_select->window_specs;
+  List<Window_spec> curr_window_specs= 
+    List<Window_spec> (thd->lex->current_select->window_specs);
   List_iterator_fast<Window_spec> it(curr_window_specs);
   Window_spec *win_spec;
   while((win_spec= it++))