Function array_set_slice

src/backend/utils/adt/arrayfuncs.c:2820–3145

* array_set_slice : * This routine sets the value of a range of array locations (specified * by upper and lower subscript values) to new values passed as * another array. * * This handles both ordinary varlena arrays and fixed-length arrays. * * Inputs: * arraydatum: the initial array object (mustn't be NULL) * nSubscripts: number of subscripts supplied (must be same for upper/lo

 * rather than returning a NULL or empty array as the fetch operations do.
 */
Datum
array_set_slice(Datum arraydatum,
				int nSubscripts,
				int *upperIndx,
				int *lowerIndx,
				bool *upperProvided,
				bool *lowerProvided,
				Datum srcArrayDatum,
				bool isNull,
				int arraytyplen,
				int elmlen,
				bool elmbyval,
				char elmalign)
{
	ArrayType  *array;
	ArrayType  *srcArray;
	ArrayType  *newarray;
	int			i,
				ndim,
				dim[MAXDIM],
				lb[MAXDIM],
				span[MAXDIM];
	bool		newhasnulls;
	int			nitems,
				nsrcitems,
				olddatasize,
				newsize,
				olditemsize,
				newitemsize,
				overheadlen,
				oldoverheadlen,
				addedbefore,
				addedafter,
				lenbefore,
				lenafter,
				itemsbefore,
				itemsafter,
				nolditems;

	/* Currently, assignment from a NULL source array is a no-op */
	if (isNull)
		return arraydatum;

	if (arraytyplen > 0)
	{
		/*
		 * fixed-length arrays -- not got round to doing this...
		 */
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("updates on slices of fixed-length arrays not implemented")));
	}

	/* detoast arrays if necessary */
	array = DatumGetArrayTypeP(arraydatum);
	srcArray = DatumGetArrayTypeP(srcArrayDatum);

	/* note: we assume srcArray contains no toasted elements */