1 files changed, 260 insertions, 0 deletions
diff --git a/sql/sql_window.h b/sql/sql_window.h
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+++ b/sql/sql_window.h
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+/*
+   Copyright (c) 2016, 2022 MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#ifndef SQL_WINDOW_INCLUDED
+#define SQL_WINDOW_INCLUDED
+
+#include "filesort.h"
+
+class Item_window_func;
+
+/*
+  Window functions module. 
+  
+  Each instance of window function has its own element in SELECT_LEX::window_specs.
+*/
+
+
+class Window_frame_bound : public Sql_alloc
+{
+
+public:
+ 
+  enum Bound_precedence_type
+  {
+    PRECEDING,
+    CURRENT,           // Used for CURRENT ROW window frame bounds
+    FOLLOWING
+  };
+
+  Bound_precedence_type precedence_type;
+ 
+
+  /* 
+    For UNBOUNDED PRECEDING / UNBOUNDED FOLLOWING window frame bounds
+    precedence type is seto to PRECEDING / FOLLOWING and
+    offset is set to NULL. 
+    The offset is not meaningful with precedence type CURRENT 
+  */
+  Item *offset;
+
+  Window_frame_bound(Bound_precedence_type prec_type,
+                     Item *offset_val)
+    : precedence_type(prec_type), offset(offset_val) {}
+
+  bool is_unbounded() { return offset == NULL; }
+
+  void print(String *str, enum_query_type query_type);
+
+};
+
+
+class Window_frame : public Sql_alloc
+{
+  
+public:
+
+  enum Frame_units
+  {
+    UNITS_ROWS,
+    UNITS_RANGE
+  };
+
+  enum Frame_exclusion
+  {
+    EXCL_NONE,
+    EXCL_CURRENT_ROW,
+    EXCL_GROUP,
+    EXCL_TIES
+  };
+
+  Frame_units units;
+
+  Window_frame_bound *top_bound;
+
+  Window_frame_bound *bottom_bound;
+
+  Frame_exclusion exclusion;
+
+  Window_frame(Frame_units win_frame_units,
+               Window_frame_bound *win_frame_top_bound,
+               Window_frame_bound *win_frame_bottom_bound,
+               Frame_exclusion win_frame_exclusion)
+    : units(win_frame_units), top_bound(win_frame_top_bound),
+      bottom_bound(win_frame_bottom_bound), exclusion(win_frame_exclusion) {}
+
+  bool check_frame_bounds();
+
+  void print(String *str, enum_query_type query_type);
+
+};
+
+class Window_spec : public Sql_alloc
+{
+  bool window_names_are_checked;
+ public:
+  virtual ~Window_spec() = default;
+
+  LEX_CSTRING *window_ref;
+
+  SQL_I_List<ORDER> *partition_list;
+  SQL_I_List<ORDER> *save_partition_list;
+
+  SQL_I_List<ORDER> *order_list;
+  SQL_I_List<ORDER> *save_order_list;
+
+  Window_frame *window_frame;
+
+  Window_spec *referenced_win_spec;
+
+  /*
+    Window_spec objects are numbered by the number of their appearance in the
+    query. This is used by compare_order_elements() to provide a predictable
+    ordering of PARTITION/ORDER BY clauses.
+  */
+  int win_spec_number;
+
+  Window_spec(LEX_CSTRING *win_ref, SQL_I_List<ORDER> *part_list,
+              SQL_I_List<ORDER> *ord_list, Window_frame *win_frame)
+    : window_names_are_checked(false), window_ref(win_ref),
+      partition_list(part_list), save_partition_list(NULL),
+      order_list(ord_list), save_order_list(NULL),
+      window_frame(win_frame), referenced_win_spec(NULL) {}
+
+  virtual const char *name() { return NULL; }
+
+  bool check_window_names(List_iterator_fast<Window_spec> &it);
+
+  const char *window_reference()
+  {
+    return window_ref ? window_ref->str : NULL;
+  }
+
+  void join_partition_and_order_lists()
+  {
+    *(partition_list->next)= order_list->first;
+  }
+
+  void disjoin_partition_and_order_lists()
+  {
+    *(partition_list->next)= NULL;
+  }
+
+  void print(String *str, enum_query_type query_type);
+  void print_order(String *str, enum_query_type query_type);
+  void print_partition(String *str, enum_query_type query_type);
+
+};
+
+class Window_def : public Window_spec
+{
+ public:
+
+  LEX_CSTRING *window_name;
+
+  Window_def(LEX_CSTRING *win_name,
+             LEX_CSTRING *win_ref, 
+             SQL_I_List<ORDER> *part_list,
+             SQL_I_List<ORDER> *ord_list,
+             Window_frame *win_frame) 
+    : Window_spec(win_ref, part_list, ord_list, win_frame),
+      window_name(win_name) {}
+ 
+  const char *name() { return window_name->str; }
+
+};
+
+int setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
+	          List<Item> &fields, List<Item> &all_fields, 
+                  List<Window_spec> &win_specs, List<Item_window_func> &win_funcs);
+
+
+//////////////////////////////////////////////////////////////////////////////
+// Classes that make window functions computation a part of SELECT's query plan
+//////////////////////////////////////////////////////////////////////////////
+
+class Frame_cursor;
+/*
+  This handles computation of one window function.
+
+  Currently, we make a spearate filesort() call for each window function.
+*/
+
+class Window_func_runner : public Sql_alloc
+{
+public:
+  /* Add the function to be computed during the execution pass  */
+  bool add_function_to_run(Item_window_func *win_func);
+
+  /* Compute and fill the fields in the table. */
+  bool exec(THD *thd, TABLE *tbl, SORT_INFO *filesort_result);
+
+private:
+  /* A list of window functions for which this Window_func_runner will compute
+     values during the execution phase. */
+  List<Item_window_func> window_functions;
+};
+
+
+/*
+  Represents a group of window functions that require the same sorting of 
+  rows and so share the filesort() call.
+
+*/
+
+class Window_funcs_sort : public Sql_alloc
+{
+public:
+  bool setup(THD *thd, SQL_SELECT *sel, List_iterator<Item_window_func> &it,
+             st_join_table *join_tab);
+  bool exec(JOIN *join, bool keep_filesort_result);
+  void cleanup() { delete filesort; }
+
+  friend class Window_funcs_computation;
+
+private:
+  Window_func_runner runner;
+
+  /* Window functions can be computed over this sorting */
+  Filesort *filesort;
+};
+
+
+struct st_join_table;
+class Explain_aggr_window_funcs;
+
+/*
+  This is a "window function computation phase": a single object of this class
+  takes care of computing all window functions in a SELECT.
+
+  - JOIN optimizer is exected to call setup() during query optimization.
+  - JOIN::exec() should call exec() once it has collected join output in a
+    temporary table.
+*/
+
+class Window_funcs_computation : public Sql_alloc
+{
+  List<Window_funcs_sort> win_func_sorts;
+public:
+  bool setup(THD *thd, List<Item_window_func> *window_funcs, st_join_table *tab);
+  bool exec(JOIN *join, bool keep_last_filesort_result);
+
+  Explain_aggr_window_funcs *save_explain_plan(MEM_ROOT *mem_root, bool is_analyze);
+  void cleanup();
+};
+
+
+#endif /* SQL_WINDOW_INCLUDED */