src/include/windowapi.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * windowapi.h
   4  *        API for window functions to extract data from their window
   5  *
   6  * A window function does not receive its arguments in the normal way
   7  * (and therefore the concept of strictness is irrelevant).  Instead it
   8  * receives a "WindowObject", which it can fetch with PG_WINDOW_OBJECT()
   9  * (note V1 calling convention must be used).  Correct call context can
  10  * be tested with WindowObjectIsValid().  Although argument values are
  11  * not passed, the call is correctly set up so that PG_NARGS() can be
  12  * used and argument type information can be obtained with
  13  * get_fn_expr_argtype(), get_fn_expr_arg_stable(), etc.
  14  *
  15  * Operations on the WindowObject allow the window function to find out
  16  * the current row number, total number of rows in the partition, etc
  17  * and to evaluate its argument expression(s) at various rows in the
  18  * window partition.  See the header comments for each WindowObject API
  19  * function in nodeWindowAgg.c for details.
  20  *
  21  *
  22  * Portions Copyright (c) 2000-2021, PostgreSQL Global Development Group
  23  *
  24  * src/include/windowapi.h
  25  *
  26  *-------------------------------------------------------------------------
  27  */
  28 #ifndef WINDOWAPI_H
  29 #define WINDOWAPI_H
  30
  31 /* values of "seektype" */
  32 #define WINDOW_SEEK_CURRENT 0
  33 #define WINDOW_SEEK_HEAD 1
  34 #define WINDOW_SEEK_TAIL 2
  35
  36 /* this struct is private in nodeWindowAgg.c */
  37 typedef struct WindowObjectData *WindowObject;
  38
  39 #define PG_WINDOW_OBJECT() ((WindowObject) fcinfo->context)
  40
  41 #define WindowObjectIsValid(winobj) \
  42         ((winobj) != NULL && IsA(winobj, WindowObjectData))
  43
  44 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
  45
  46 extern int64 WinGetCurrentPosition(WindowObject winobj);
  47 extern int64 WinGetPartitionRowCount(WindowObject winobj);
  48
  49 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
  50
  51 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
  52
  53 extern Datum WinGetFuncArgInPartition(WindowObject winobj, int argno,
  54                                                                           int relpos, int seektype, bool set_mark,
  55                                                                           bool *isnull, bool *isout);
  56
  57 extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
  58                                                                   int relpos, int seektype, bool set_mark,
  59                                                                   bool *isnull, bool *isout);
  60
  61 extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
  62                                                                   bool *isnull);
  63
  64 #endif                                                  /* WINDOWAPI_H */