1 files changed, 64 insertions, 0 deletions
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
new file mode 100644
index 0000000..e8c9fc5
--- /dev/null
+++ b/src/include/windowapi.h
@@ -0,0 +1,64 @@
+/*-------------------------------------------------------------------------
+ *
+ * windowapi.h
+ *	  API for window functions to extract data from their window
+ *
+ * A window function does not receive its arguments in the normal way
+ * (and therefore the concept of strictness is irrelevant).  Instead it
+ * receives a "WindowObject", which it can fetch with PG_WINDOW_OBJECT()
+ * (note V1 calling convention must be used).  Correct call context can
+ * be tested with WindowObjectIsValid().  Although argument values are
+ * not passed, the call is correctly set up so that PG_NARGS() can be
+ * used and argument type information can be obtained with
+ * get_fn_expr_argtype(), get_fn_expr_arg_stable(), etc.
+ *
+ * Operations on the WindowObject allow the window function to find out
+ * the current row number, total number of rows in the partition, etc
+ * and to evaluate its argument expression(s) at various rows in the
+ * window partition.  See the header comments for each WindowObject API
+ * function in nodeWindowAgg.c for details.
+ *
+ *
+ * Portions Copyright (c) 2000-2020, PostgreSQL Global Development Group
+ *
+ * src/include/windowapi.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef WINDOWAPI_H
+#define WINDOWAPI_H
+
+/* values of "seektype" */
+#define WINDOW_SEEK_CURRENT 0
+#define WINDOW_SEEK_HEAD 1
+#define WINDOW_SEEK_TAIL 2
+
+/* this struct is private in nodeWindowAgg.c */
+typedef struct WindowObjectData *WindowObject;
+
+#define PG_WINDOW_OBJECT() ((WindowObject) fcinfo->context)
+
+#define WindowObjectIsValid(winobj) \
+	((winobj) != NULL && IsA(winobj, WindowObjectData))
+
+extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
+
+extern int64 WinGetCurrentPosition(WindowObject winobj);
+extern int64 WinGetPartitionRowCount(WindowObject winobj);
+
+extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
+
+extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
+
+extern Datum WinGetFuncArgInPartition(WindowObject winobj, int argno,
+									  int relpos, int seektype, bool set_mark,
+									  bool *isnull, bool *isout);
+
+extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout);
+
+extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
+								  bool *isnull);
+
+#endif							/* WINDOWAPI_H */