MDEV-9526: Compute Aggregate functions as window functions

- Add temporary code: clone_read_record() clones READ_RECORD structure,
  as long as it is used for reading filesort() result that fits into
  memory.
- Add frame bounds for ROWS-type frames. ROWS n PRECEDING|FOLLOWING,
  ROWS UNBOUNDED PRECEDING|FOLLOWING, CURRENT ROW are supported.
- Add Item_sum_count::remove() which allows "streaming" computation
  of COUNT() over a moving frame.

mysql-test/r/win.result

@@ -136,3 +136,120 @@ pk	a	b	rank() over (partition by b order by a)	dense_rank() over (partition by b
 9	4	20	4	2
 10	4	20	4	2
 drop table t3;
+#
+# Try Aggregates as window functions. With frames.
+#
+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
+select 
+pk, c, 
+count(*) over (partition by c order by pk 
+rows between 2 preceding and 2 following) as CNT
+from t1;
+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
+select 
+pk, c, 
+count(*) over (partition by c order by pk 
+rows between 1 preceding and 2 following) as CNT
+from t1;
+pk	c	CNT
+1	1	3
+2	1	4
+3	1	3
+4	1	2
+5	2	3
+6	2	4
+7	2	4
+8	2	4
+9	2	3
+10	2	2
+select
+pk, c,  
+count(*) over (partition by c order by pk
+rows between 2 preceding and current row) as CNT 
+from t1;
+pk	c	CNT
+1	1	1
+2	1	2
+3	1	3
+4	1	3
+5	2	1
+6	2	2
+7	2	3
+8	2	3
+9	2	3
+10	2	3
+select 
+pk,c, 
+count(*) over (partition by c order by pk rows
+between 1 following and 2 following) as CNT
+from t1;
+pk	c	CNT
+1	1	2
+2	1	2
+3	1	1
+4	1	0
+5	2	2
+6	2	2
+7	2	2
+8	2	2
+9	2	1
+10	2	0
+select 
+pk,c, 
+count(*) over (partition by c order by pk rows
+between 2 preceding and 1 preceding) as CNT
+from t1;
+pk	c	CNT
+1	1	0
+2	1	1
+3	1	2
+4	1	2
+5	2	0
+6	2	1
+7	2	2
+8	2	2
+9	2	2
+10	2	2
+select
+pk, c,  
+count(*) over (partition by c order by pk
+rows between current row and 1 following) as CNT 
+from t1;
+pk	c	CNT
+1	1	2
+2	1	2
+3	1	2
+4	1	1
+5	2	2
+6	2	2
+7	2	2
+8	2	2
+9	2	2
+10	2	1
+drop table t0,t1;

mysql-test/t/win.test

@@ -110,3 +110,52 @@ select pk, a, b, rank() over (order by a), dense_rank() over (order by a) from t
 select pk, a, b, rank() over (partition by b order by a), dense_rank() over (partition by b order by a) from t3;
 
 drop table t3;
+
+--echo #
+--echo # Try Aggregates as window functions. With frames.
+--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;
+
+select 
+  pk, c, 
+  count(*) over (partition by c order by pk 
+                 rows between 2 preceding and 2 following) as CNT
+from t1;
+
+select 
+  pk, c, 
+  count(*) over (partition by c order by pk 
+                 rows between 1 preceding and 2 following) as CNT
+from t1;
+
+select
+  pk, c,  
+  count(*) over (partition by c order by pk
+                 rows between 2 preceding and current row) as CNT 
+from t1;
+
+select 
+  pk,c, 
+  count(*) over (partition by c order by pk rows
+                 between 1 following and 2 following) as CNT
+from t1;
+
+select 
+  pk,c, 
+  count(*) over (partition by c order by pk rows
+                 between 2 preceding and 1 preceding) as CNT
+from t1;
+
+select
+  pk, c,  
+  count(*) over (partition by c order by pk
+                 rows between current row and 1 following) as CNT 
+from t1;
+drop table t0,t1;
+

sql/item_sum.cc

@@ -1531,6 +1531,18 @@ bool Item_sum_count::add()
   return 0;
 }
 
+
+/*
+  Remove a row. This is used by window functions.
+*/
+
+void Item_sum_count::remove()
+{
+  /* TODO: Handle DECIMAL type */
+  DBUG_ASSERT(aggr->Aggrtype() == Aggregator::SIMPLE_AGGREGATOR);
+  count--;
+}
+
 longlong Item_sum_count::val_int()
 {
   DBUG_ASSERT(fixed == 1);

sql/item_sum.h

@@ -545,6 +545,9 @@ public:
   virtual void clear()= 0;
   virtual bool add()= 0;
   virtual bool setup(THD *thd) { return false; }
+  
+  //psergey: for window functions:
+  virtual void remove() { DBUG_ASSERT(0); }
 
   virtual void cleanup();
   bool check_vcol_func_processor(uchar *int_arg) 
@@ -784,6 +787,8 @@ class Item_sum_count :public Item_sum_int
   void clear();
   bool add();
   void cleanup();
+  // psergey-added:
+  void remove();
 
   public:
   Item_sum_count(THD *thd, Item *item_par):

sql/item_windowfunc.cc

@@ -18,6 +18,8 @@ Item_window_func::fix_fields(THD *thd, Item **ref)
   if (window_func->fix_fields(thd, ref))
     return TRUE;
 
+  max_length= window_func->max_length;
+
   fixed= 1;
   force_return_blank= true;
   read_value_from_result_field= false;
@@ -88,10 +90,14 @@ bool Item_sum_rank::add()
   return false; 
 }
 
+int Item_window_func::check_partition_bound()
+{
+  return test_if_group_changed(partition_fields);
+}
 
-void Item_window_func::advance_window() {
+void Item_window_func::advance_window()
-
+{
-  int changed = test_if_group_changed(partition_fields);
+  int changed= check_partition_bound();
 
   if (changed > -1)
   {

sql/item_windowfunc.h

@@ -275,6 +275,7 @@ class Item_sum_cume_dist: public Item_sum_num
 class Item_window_func : public Item_result_field
 {
   /* Window function parameters as we've got them from the parser */
+public:
   Item_sum *window_func;
   LEX_STRING *window_name;
 public:
@@ -301,10 +302,12 @@ public:
 
   /*
     Computation functions.
+    TODO: consoder merging these with class Group_bound_tracker.
   */
   void setup_partition_border_check(THD *thd);
 
   void advance_window();
+  int check_partition_bound();
 
   enum_field_types field_type() const { return window_func->field_type(); }
   enum Item::Type type() const { return Item::WINDOW_FUNC_ITEM; }
@@ -367,12 +370,18 @@ public:
   my_decimal* val_decimal(my_decimal* dec)
   { 
     if (force_return_blank)
+    {
+      my_decimal_set_zero(dec);
       return dec;
+    }
     return read_value_from_result_field? result_field->val_decimal(dec) : 
                                          window_func->val_decimal(dec);
   }
 
-  void fix_length_and_dec() { }
+  void fix_length_and_dec()
+  {
+    window_func->fix_length_and_dec();
+  }
 
   const char* func_name() const { return "WF"; }
 

sql/records.cc

@@ -39,7 +39,7 @@ int rr_sequential(READ_RECORD *info);
 static int rr_from_tempfile(READ_RECORD *info);
 static int rr_unpack_from_tempfile(READ_RECORD *info);
 static int rr_unpack_from_buffer(READ_RECORD *info);
-static int rr_from_pointers(READ_RECORD *info);
+int rr_from_pointers(READ_RECORD *info);
 static int rr_from_cache(READ_RECORD *info);
 static int init_rr_cache(THD *thd, READ_RECORD *info);
 static int rr_cmp(uchar *a,uchar *b);
@@ -531,8 +531,8 @@ static int rr_unpack_from_tempfile(READ_RECORD *info)
 
   return 0;
 }
-
+//psergey: make this 'static' again:
-static int rr_from_pointers(READ_RECORD *info)
+int rr_from_pointers(READ_RECORD *info)
 {
   int tmp;
   uchar *cache_pos;

sql/sql_window.cc

@@ -4,7 +4,6 @@
 #include "sql_base.h"
 #include "sql_window.h"
 
-//TODO: why pass List<Window_spec> by value??
 
 bool
 Window_spec::check_window_names(List_iterator_fast<Window_spec> &it)
@@ -83,6 +82,481 @@ setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
 }
 
 
+/*
+  Do a pass over sorted table and compute window function values.
+
+  This function is for handling window functions that can be computed on the
+  fly. Examples are RANK() and ROW_NUMBER().
+*/
+bool compute_window_func_values(Item_window_func *item_win, 
+                                TABLE *tbl, READ_RECORD *info)
+{
+  int err;
+  while (!(err=info->read_record(info)))
+  {
+    store_record(tbl,record[1]);
+    
+    /* 
+      This will cause window function to compute its value for the
+      current row :
+    */
+    item_win->advance_window();
+
+    /*
+      Put the new value into temptable's field
+      TODO: Should this use item_win->update_field() call?
+      Regular aggegate function implementations seem to implement it.
+    */
+    item_win->save_in_field(item_win->result_field, true);
+    err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
+    if (err && err != HA_ERR_RECORD_IS_THE_SAME)
+      return true;
+  }
+  return false;
+}
+
+/////////////////////////////////////////////////////////////////////////////
+// Window Frames support 
+/////////////////////////////////////////////////////////////////////////////
+
+// note: make rr_from_pointers static again when not need it here anymore
+int rr_from_pointers(READ_RECORD *info);
+
+/*
+  A temporary way to clone READ_RECORD structures until Monty provides the real
+  one.
+*/
+bool clone_read_record(const READ_RECORD *src, READ_RECORD *dst)
+{
+  DBUG_ASSERT(src->table->sort.record_pointers);
+  DBUG_ASSERT(src->read_record == rr_from_pointers);
+  memcpy(dst, src, sizeof(READ_RECORD));
+  return false;
+}
+
+
+/* A wrapper around test_if_group_changed */
+class Group_bound_tracker
+{
+  List<Cached_item> group_fields;
+public:
+  void init(THD *thd, SQL_I_List<ORDER> *list)
+  {
+    for (ORDER *curr = list->first; curr; curr=curr->next) 
+    {
+      Cached_item *tmp= new_Cached_item(thd, curr->item[0], TRUE);  
+      group_fields.push_back(tmp);
+    }
+  }
+
+  bool check_if_next_group()
+  {
+    if (test_if_group_changed(group_fields) > -1)
+      return true;
+    return false;
+  }
+};
+
+
+/*
+  Window frame bound cursor. Abstract interface.
+  
+  @detail
+    The cursor moves within the partition that the current row is in.
+    It may be ahead or behind the current row.
+
+    The cursor also assumes that the current row moves forward through the
+    partition and will move to the next adjacent partition after this one.
+
+  @todo
+  - if we want to allocate this on the MEM_ROOT we should make sure 
+    it is not re-allocated for every subquery execution.
+*/
+
+class Frame_cursor : public Sql_alloc
+{
+public:
+  virtual void init(THD *thd, READ_RECORD *info, 
+                    SQL_I_List<ORDER> *partition_list)
+  {}
+
+  /*
+    Current row has entered the new partition (this also includes the first
+    partition).
+    //TODO: can we also say "tbl->record[0] is the first row in the partition?"
+    // TODO2: and if yes, will this function keep it so? (NO)
+
+    Position the frame bound accordingly.
+  */
+  virtual void next_partition(bool first, Item_sum* item)=0;
+  
+  /*
+    The current row has moved one row forward.
+    Move this frame bound accordingly, and update the value of aggregate
+    function as necessary.
+  */
+  virtual void next_row(Item_sum* item)=0;
+  
+  virtual ~Frame_cursor(){}
+};
+
+
+/*
+  UNBOUNDED (PRECEDING|FOLLOWING) frame bound
+*/
+
+class Frame_unbounded : public Frame_cursor
+{
+  const bool is_start;
+  const bool is_preceding;
+  
+  READ_RECORD cursor;
+  Group_bound_tracker bound_tracker;
+public:
+  Frame_unbounded(bool is_start_arg, bool is_preceding_arg) : 
+    is_start(is_start_arg), is_preceding(is_preceding_arg)
+  {}
+
+  void init(THD *thd, READ_RECORD *info, SQL_I_List<ORDER> *partition_list)
+  {
+    if (!is_preceding)
+    {
+      // Cursor is only needed by UNBOUNDED FOLLOWING
+      clone_read_record(info, &cursor);
+      bound_tracker.init(thd, partition_list);
+    }
+  }
+
+  void next_partition(bool first, Item_sum* item)
+  {
+    if (is_preceding)
+    {
+      /* 
+        UNBOUNDED PRECEDING frame end just stays on the first row.
+        We are start of the frame, so we don't need to update the sum function.
+      */
+    }
+    else
+    {
+      /*
+        UNBOUNDED FOLLOWING should reach the end of the partition and stay
+        there.
+      */
+      if (first)
+      {
+        /* Read the first row */
+        if (cursor.read_record(&cursor))
+          return;
+      }
+      /* Remember what partition we are in */
+      bound_tracker.check_if_next_group();
+
+      item->add();
+
+      while (!cursor.read_record(&cursor))
+      {
+        if (bound_tracker.check_if_next_group())
+          break;
+        item->add();
+      }
+    }
+  }
+
+  void next_row(Item_sum* item)
+  {
+    /* Do nothing, UNBOUNDED PRECEDING|FOLLOWING frame ends don't move. */
+  }
+};
+
+
+/*
+  ROWS $n (PRECEDING|FOLLOWING) frame bound.
+*/
+
+class Frame_n_rows : public Frame_cursor
+{
+  /* Whether this start of frame or end of rame */
+  const bool is_start;
+  const ha_rows n_rows;
+  const bool is_preceding;
+
+  ha_rows n_rows_to_skip;
+
+  READ_RECORD cursor;
+  bool cursor_eof;
+
+  Group_bound_tracker bound_tracker;
+  bool at_partition_start;
+  bool at_partition_end;
+public:
+  Frame_n_rows(bool is_start_arg, bool is_preceding_arg, ha_rows n_rows_arg) :
+    is_start(is_start_arg), n_rows(n_rows_arg), is_preceding(is_preceding_arg)
+  {}
+
+  void init(THD *thd, READ_RECORD *info, SQL_I_List<ORDER> *partition_list)
+  {
+    clone_read_record(info, &cursor);
+    cursor_eof= false;
+    at_partition_start= true;
+    bound_tracker.init(thd, partition_list);
+  }
+
+  void next_partition(bool first, Item_sum* item)
+  {
+    cursor_eof= false;
+    at_partition_start= true;
+    at_partition_end= false;
+    if (is_preceding)
+    {
+      if (!first)
+      {
+        /* 
+          The cursor in "ROWS n PRECEDING" lags behind by n_rows rows.
+          Catch up.
+        */
+        while (!(cursor_eof= (0 != cursor.read_record(&cursor))))
+        {
+          if (bound_tracker.check_if_next_group())
+            break;
+        }
+      }
+      n_rows_to_skip= n_rows - (is_start? 0:1);
+    }
+    else
+    {
+      /* 
+        "ROWS n FOLLOWING" is already at the first row in the next partition.
+        Move it to be n_rows ahead.
+      */
+      n_rows_to_skip= 0;
+
+      if (!first && (!is_start || n_rows))
+      {
+          // We are positioned at the first row in the partition:
+        if (is_start) // this is frame start endpoint
+          item->remove();
+        else
+          item->add();
+      }
+      /* 
+        Note: i_end=-1 when this is a start-endpoint "CURRENT ROW" which is
+              implemented as "ROWS 0 FOLLOWING".
+     */
+      longlong i_end= n_rows + (first?1:0)- is_start;
+      for (longlong i= 0; i < i_end; i++)
+      {
+        if (next_row_intern(item))
+          break;
+      }
+    }
+  }
+  
+  void next_row(Item_sum* item)
+  {
+    if (n_rows_to_skip)
+    {
+      n_rows_to_skip--;
+      return;
+    }
+    if (at_partition_end)
+      return;
+    next_row_intern(item);
+  }
+
+private:
+  bool next_row_intern(Item_sum *item)
+  {
+    if (!cursor_eof)
+    {
+      if (!(cursor_eof= (0 != cursor.read_record(&cursor))))
+      {
+        bool new_group= bound_tracker.check_if_next_group();
+        if (at_partition_start || !new_group)
+        {
+          if (is_start) // this is frame start endpoint
+            item->remove();
+          else
+            item->add();
+
+          at_partition_start= false;
+          return false; /* Action done */
+        }
+        else
+        {
+          at_partition_end= true;
+          return true;
+        }
+      }
+    }
+    return true; /* Action not done */
+  }
+};
+
+
+/* CURRENT ROW is the same as "ROWS 0 FOLLOWING" */
+class Frame_current_row : public Frame_n_rows
+{
+public:
+  Frame_current_row(bool is_start_arg) :
+    Frame_n_rows(is_start_arg, false /*is_preceding*/, ha_rows(0))
+  {}
+};
+
+
+Frame_cursor *get_frame_cursor(Window_frame_bound *bound, bool is_start_bound)
+{
+  if (bound->precedence_type == Window_frame_bound::PRECEDING ||
+      bound->precedence_type == Window_frame_bound::FOLLOWING) 
+  {
+    bool is_preceding= (bound->precedence_type ==
+                        Window_frame_bound::PRECEDING);
+    if (bound->offset == NULL)
+    {
+      return new Frame_unbounded(is_start_bound, is_preceding);
+    }
+
+    longlong n_rows= bound->offset->val_int();
+    return new Frame_n_rows(is_start_bound, is_preceding, n_rows);
+  }
+
+  if (bound->precedence_type == Window_frame_bound::CURRENT)
+  {
+    return new Frame_current_row(is_start_bound);
+  }
+  return NULL; 
+}
+
+
+/*
+  Streamed window function computation with window frames.
+
+  We make a single pass over the ordered temp.table, but we're using three
+  cursors: 
+   - current row - the row that we're computing window func value for)
+   - start_bound - the start of the frame
+   - end_bound   - the end of the frame
+   
+  All three cursors move together.
+
+  @todo
+    Provided bounds have their 'cursors'... is it better to re-clone their
+    cursors or re-position them onto the current row?
+
+  @detail
+    ROWS BETWEEN 3 PRECEDING  -- frame start
+              AND 3 FOLLOWING  -- frame end
+     
+                                    /------ frame end (aka BOTTOM)
+    Dataset start                   |
+     --------====*=======[*]========*========-------->> dataset end
+                 |        \  
+                 |         +-------- current row
+                 |
+                 \-------- frame start ("TOP")
+  
+    - frame_end moves forward and adds rows into the aggregate function.
+    - frame_start follows behind and removes rows from the aggregate function.
+    - current_row is the row where the value of aggregate function is stored.
+
+  @TODO:  Only the first cursor needs to check for run-out-of-partition
+  condition (Others can catch up by counting rows?)
+
+*/
+
+bool compute_window_func_with_frames(Item_window_func *item_win,
+                                     TABLE *tbl, READ_RECORD *info)
+{
+  THD *thd= current_thd;
+  int err= 0;
+  Frame_cursor *start_bound;
+  Frame_cursor *end_bound;
+
+  Item_sum *sum_func= item_win->window_func;
+  /* This algorithm doesn't support DISTINCT aggregator */
+  sum_func->set_aggregator(Aggregator::SIMPLE_AGGREGATOR);
+  
+  Window_frame *window_frame= item_win->window_spec->window_frame;
+  DBUG_ASSERT(window_frame->units == Window_frame::UNITS_ROWS);
+  start_bound= get_frame_cursor(window_frame->top_bound, true);
+  end_bound= get_frame_cursor(window_frame->bottom_bound, false);
+    
+  start_bound->init(thd, info, &item_win->window_spec->partition_list);
+  end_bound->init(thd, info, &item_win->window_spec->partition_list);
+
+  bool is_error= false;
+  bool first_row= true;
+  uchar *rowid_buf= (uchar*) my_malloc(tbl->file->ref_length, MYF(0));
+
+  while (true)
+  {
+    if (first_row)
+    {
+      /* Start the first partition */
+      sum_func->clear();
+      end_bound->next_partition(true, sum_func);
+      start_bound->next_partition(true, sum_func);
+    }
+    else
+    {
+      /* These can write into tbl->record[0] */
+      end_bound->next_row(sum_func);
+      start_bound->next_row(sum_func);
+    }
+    
+    if ((err=info->read_record(info)))
+    {
+      /* End of file */
+      break;
+    }
+    
+    store_record(tbl,record[1]);
+    bool partition_changed= (item_win->check_partition_bound() > -1)? true:
+                                                                     false;
+    if (!first_row && partition_changed) 
+    {
+      sum_func->clear();
+      tbl->file->position(tbl->record[0]);     
+      memcpy(rowid_buf, tbl->file->ref, tbl->file->ref_length);
+      /* 
+        Ok, the current row is the first row in the new partition.
+        We move end_bound first, because we want rows to be added into the
+        aggregate before start_bound attempts to remove them.
+      */
+      end_bound->next_partition(false, sum_func);
+      
+      /*
+        The problem is, the above call may have made tbl->record[0] to point to
+        some other record.
+      */
+      tbl->file->ha_rnd_pos(tbl->record[0], rowid_buf);
+      start_bound->next_partition(false, sum_func);
+
+      /* 
+        The same problem again. The above call may have moved table's current
+        record. We need to make the current row current, so that ha_update_row
+        call below updates the right row.
+      */
+      tbl->file->ha_rnd_pos(tbl->record[0], rowid_buf);
+    }
+    first_row= false;
+    
+    /* Read the current row and update it */
+    item_win->save_in_field(item_win->result_field, true);
+    err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
+    if (err && err != HA_ERR_RECORD_IS_THE_SAME)
+    {
+      is_error= true;
+      break;
+    }
+  }
+
+  my_free(rowid_buf);
+  delete start_bound;
+  delete end_bound;
+  return is_error? true: false;
+}
+
+
 /*
   @brief
     This function is called by JOIN::exec to compute window function values
@@ -264,30 +738,34 @@ bool JOIN::process_window_functions(List<Item> *curr_fields_list)
         TABLE *tbl= join_tab[top_join_tab_count].table;
         if (init_read_record(&info, thd, tbl, select, 0, 1, FALSE))
           return true;
-
+        bool is_error= false;
+        
         item_win->setup_partition_border_check(thd);
-
+      
-        int err;
+        Item_sum::Sumfunctype type= item_win->window_func->sum_func();
-        while (!(err=info.read_record(&info)))
+        if (type == Item_sum::ROW_NUMBER_FUNC ||
+            type == Item_sum::RANK_FUNC || 
+            type == Item_sum::DENSE_RANK_FUNC)
         {
-          store_record(tbl,record[1]);
-          
           /* 
-            This will cause window function to compute its value for the
+            One-pass window function computation, walk through the rows and
-            current row :
+            assign values.
           */
-          item_win->advance_window();
+          if (compute_window_func_values(item_win, tbl, &info))
-
+            is_error= true;
-          /*
-            Put the new value into temptable's field
-            TODO: Should this use item_win->update_field() call?
-            Regular aggegate function implementations seem to implement it.
-          */
-          item_win->save_in_field(item_win->result_field, true);
-          err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
-          if (err && err != HA_ERR_RECORD_IS_THE_SAME)
-            return true;
         }
+        else if (type == Item_sum::COUNT_FUNC)
+        {
+          /*
+            Frame-aware window function computation. It does one pass, but 
+            uses three cursors -frame_start, current_row, and frame_end.
+          */
+          if (compute_window_func_with_frames(item_win, tbl, &info))
+            is_error= true;
+        }
+        else
+          DBUG_ASSERT(0);
+
         item_win->set_read_value_from_result_field();
         /* This calls filesort_free_buffers(): */
         end_read_record(&info);
@@ -295,6 +773,9 @@ bool JOIN::process_window_functions(List<Item> *curr_fields_list)
         delete join_tab[top_join_tab_count].filesort;
         join_tab[top_join_tab_count].filesort= NULL;
         free_io_cache(tbl);
+
+        if (is_error)
+          return true;
       }
     }
   }