Function array_create_iterator

src/backend/utils/adt/arrayfuncs.c:4486–4557

* array_create_iterator --- set up to iterate through an array * * If slice_ndim is zero, we will iterate element-by-element; the returned * datums are of the array's element type. * * If slice_ndim is 1..ARR_NDIM(arr), we will iterate by slices: the * returned datums are of the same array type as 'arr', but of size * equal to the rightmost N dimensions of 'arr'. * * The passed-in array m

 * The passed-in array must remain valid for the lifetime of the iterator.
 */
ArrayIterator
array_create_iterator(ArrayType *arr, int slice_ndim, ArrayMetaState *mstate)
{
	ArrayIterator iterator = palloc0(sizeof(ArrayIteratorData));

	/*
	 * Sanity-check inputs --- caller should have got this right already
	 */
	Assert(PointerIsValid(arr));
	if (slice_ndim < 0 || slice_ndim > ARR_NDIM(arr))
		elog(ERROR, "invalid arguments to array_create_iterator");

	/*
	 * Remember basic info about the array and its element type
	 */
	iterator->arr = arr;
	iterator->nullbitmap = ARR_NULLBITMAP(arr);
	iterator->nitems = ArrayGetNItems(ARR_NDIM(arr), ARR_DIMS(arr));

	if (mstate != NULL)
	{
		Assert(mstate->element_type == ARR_ELEMTYPE(arr));

		iterator->typlen = mstate->typlen;
		iterator->typbyval = mstate->typbyval;
		iterator->typalign = mstate->typalign;
	}
	else
		get_typlenbyvalalign(ARR_ELEMTYPE(arr),
							 &iterator->typlen,
							 &iterator->typbyval,
							 &iterator->typalign);

	/*
	 * Remember the slicing parameters.
	 */
	iterator->slice_ndim = slice_ndim;

	if (slice_ndim > 0)
	{
		/*
		 * Get pointers into the array's dims and lbound arrays to represent
		 * the dims/lbound arrays of a slice.  These are the same as the
		 * rightmost N dimensions of the array.
		 */
		iterator->slice_dims = ARR_DIMS(arr) + ARR_NDIM(arr) - slice_ndim;
		iterator->slice_lbound = ARR_LBOUND(arr) + ARR_NDIM(arr) - slice_ndim;

		/*
		 * Compute number of elements in a slice.
		 */
		iterator->slice_len = ArrayGetNItems(slice_ndim,
											 iterator->slice_dims);

		/*
		 * Create workspace for building sub-arrays.
		 */
		iterator->slice_values = (Datum *)