Function construct_md_array

src/backend/utils/adt/arrayfuncs.c:3409–3534

* construct_md_array --- simple method for constructing an array object * with arbitrary dimensions and possible NULLs * * elems: array of Datum items to become the array contents * nulls: array of is-null flags (can be NULL if no nulls) * ndims: number of dimensions * dims: integer array with size of each dimension * lbs: integer array with lower bound of each dimension * elmtype, e

 * to hard-wire values if the element type is hard-wired.
 */
ArrayType *
construct_md_array(Datum *elems,
				   bool *nulls,
				   int ndims,
				   int *dims,
				   int *lbs,
				   Oid elmtype, int elmlen, bool elmbyval, char elmalign)
{
	ArrayType  *result;
	bool		hasnulls;
	int32		nbytes;
	int32		dataoffset;
	int			i;
	int			nelems;
	bool		fixedwidthtype;

	if (ndims < 0)				/* we do allow zero-dimension arrays */
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("invalid number of dimensions: %d", ndims)));
	if (ndims > MAXDIM)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
						ndims, MAXDIM)));

	/* This checks for overflow of the array dimensions */
	nelems = ArrayGetNItems(ndims, dims);
	ArrayCheckBounds(ndims, dims, lbs);

	/* if ndims <= 0 or any dims[i] == 0, return empty array */
	if (nelems <= 0)
		return construct_empty_array(elmtype);

	/* compute required space */
	nbytes = 0;

	/*   fast path for fixed width types */
	switch (elmtype) 
	{
		case INT2OID:
		case INT4OID:
		case INT8OID:
		case FLOAT4OID:
		case FLOAT8OID:
			fixedwidthtype=true;
			break;
		default:
			fixedwidthtype=false;
	}
	hasnulls = false;
	if (fixedwidthtype)
	{
		nbytes = nelems * elmlen;

		/* Still need to handle the possibility of nulls */
		if (nulls)
		{