Function initialize_windowaggregate

src/backend/executor/nodeWindowAgg.c:237–278

* initialize_windowaggregate * parallel to initialize_aggregates in nodeAgg.c */

 * parallel to initialize_aggregates in nodeAgg.c
 */
static void
initialize_windowaggregate(WindowAggState *winstate,
						   WindowStatePerFunc perfuncstate,
						   WindowStatePerAgg peraggstate)
{
	MemoryContext oldContext;

	/*
	 * If we're using a private aggcontext, we may reset it here.  But if the
	 * context is shared, we don't know which other aggregates may still need
	 * it, so we must leave it to the caller to reset at an appropriate time.
	 */
	if (peraggstate->aggcontext != winstate->aggcontext)
		MemoryContextResetAndDeleteChildren(peraggstate->aggcontext);

	if (peraggstate->initValueIsNull)
		peraggstate->transValue = peraggstate->initValue;
	else
	{
		oldContext = MemoryContextSwitchTo(peraggstate->aggcontext);
		peraggstate->transValue = datumCopy(peraggstate->initValue,
											peraggstate->transtypeByVal,
											peraggstate->transtypeLen);
		MemoryContextSwitchTo(oldContext);
	}
	peraggstate->transValueIsNull = peraggstate->initValueIsNull;
	peraggstate->transValueCount = 0;
	peraggstate->resultValue = (Datum) 0;
	peraggstate->resultValueIsNull = true;

	if (peraggstate->isDistinct)
	{
		peraggstate->distinctSortState =
			tuplesort_begin_datum(peraggstate->distinctType,
								  peraggstate->distinctLtOper,
								  peraggstate->distinctColl,
								  false, /* nullsFirstFlag */
								  PlanStateOperatorMemKB((PlanState *) winstate),
								  NULL, /* coordinate */
								  false);
	}
}

/*
 * advance_windowaggregate