Function array_set_element_expanded

src/backend/utils/adt/arrayfuncs.c:2515–2777

* Implementation of array_set_element() for an expanded array * * Note: as with any operation on a read/write expanded object, we must * take pains not to leave the object in a corrupt state if we fail partway * through. */

 * through.
 */
static Datum
array_set_element_expanded(Datum arraydatum,
						   int nSubscripts, int *indx,
						   Datum dataValue, bool isNull,
						   int arraytyplen,
						   int elmlen, bool elmbyval, char elmalign)
{
	ExpandedArrayHeader *eah;
	Datum	   *dvalues;
	bool	   *dnulls;
	int			i,
				ndim,
				dim[MAXDIM],
				lb[MAXDIM],
				offset;
	bool		dimschanged,
				newhasnulls;
	int			addedbefore,
				addedafter;
	char	   *oldValue;

	/* Convert to R/W object if not so already */
	eah = DatumGetExpandedArray(arraydatum);

	/* Sanity-check caller's info against object; we don't use it otherwise */
	Assert(arraytyplen == -1);
	Assert(elmlen == eah->typlen);
	Assert(elmbyval == eah->typbyval);
	Assert(elmalign == eah->typalign);

	/*
	 * Copy dimension info into local storage.  This allows us to modify the
	 * dimensions if needed, while not messing up the expanded value if we
	 * fail partway through.
	 */
	ndim = eah->ndims;
	Assert(ndim >= 0 && ndim <= MAXDIM);
	memcpy(dim, eah->dims, ndim * sizeof(int));
	memcpy(lb, eah->lbound, ndim * sizeof(int));
	dimschanged = false;

	/*
	 * if number of dims is zero, i.e. an empty array, create an array with
	 * nSubscripts dimensions, and set the lower bounds to the supplied
	 * subscripts.
	 */
	if (ndim == 0)
	{
		/*
		 * Allocate adequate space for new dimension info.  This is harmless
		 * if we fail later.
		 */
		Assert(nSubscripts > 0 && nSubscripts <= MAXDIM);
		eah->dims = (int *) MemoryContextAllocZero(eah->hdr.eoh_context,
												   nSubscripts * sizeof(int));
		eah->lbound = (int *) MemoryContextAllocZero(eah->hdr.eoh_context,
													 nSubscripts * sizeof(int));