Function WinGetPartitionRowCount

src/backend/executor/nodeWindowAgg.c:3459–3465

* WinGetPartitionRowCount * Return total number of rows contained in the current partition. * * Note: this is a relatively expensive operation because it forces the * whole partition to be "spooled" into the tuplestore at once. Once * executed, however, additional calls within the same partition are cheap. */

 * executed, however, additional calls within the same partition are cheap.
 */
int64
WinGetPartitionRowCount(WindowObject winobj)
{
	Assert(WindowObjectIsValid(winobj));
	spool_tuples(winobj->winstate, -1);
	return winobj->winstate->spooled_rows;
}

/*
 * WinSetMarkPosition