Function array_agg_array_combine

src/backend/utils/adt/array_userfuncs.c:1169–1318

}

Datum
array_agg_array_combine(PG_FUNCTION_ARGS)
{
	ArrayBuildStateArr *state1;
	ArrayBuildStateArr *state2;
	MemoryContext agg_context;
	MemoryContext old_context;

	if (!AggCheckCallContext(fcinfo, &agg_context))
		elog(ERROR, "aggregate function called in non-aggregate context");

	state1 = PG_ARGISNULL(0) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
	state2 = PG_ARGISNULL(1) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(1);

	if (state2 == NULL)
	{
		/*
		 * NULL state2 is easy, just return state1, which we know is already
		 * in the agg_context
		 */
		if (state1 == NULL)
			PG_RETURN_NULL();
		PG_RETURN_POINTER(state1);
	}

	if (state1 == NULL)
	{
		/* We must copy state2's data into the agg_context */
		old_context = MemoryContextSwitchTo(agg_context);

		state1 = initArrayResultArr(state2->array_type, InvalidOid,
									agg_context, false);

		state1->abytes = state2->abytes;
		state1->data = (char *) palloc(state1->abytes);

		if (state2->nullbitmap)
		{
			int			size = (state2->aitems + 7) / 8;

			state1->nullbitmap = (bits8 *) palloc(size);
			memcpy(state1->nullbitmap, state2->nullbitmap, size);
		}

		memcpy(state1->data, state2->data, state2->nbytes);
		state1->nbytes = state2->nbytes;
		state1->aitems = state2->aitems;
		state1->nitems = state2->nitems;
		state1->ndims = state2->ndims;
		memcpy(state1->dims, state2->dims, sizeof(state2->dims));
		memcpy(state1->lbs, state2->lbs, sizeof(state2->lbs));
		state1->array_type = state2->array_type;
		state1->element_type = state2->element_type;

		MemoryContextSwitchTo(old_context);

		PG_RETURN_POINTER(state1);
	}