Function ExecEvalArrayExpr

src/backend/executor/execExprInterp.c:2786–2988

* Evaluate an ARRAY[] expression. * * The individual array elements (or subarrays) have already been evaluated * into op->d.arrayexpr.elemvalues[]/elemnulls[]. */

 * into op->d.arrayexpr.elemvalues[]/elemnulls[].
 */
void
ExecEvalArrayExpr(ExprState *state, ExprEvalStep *op)
{
	ArrayType  *result;
	Oid			element_type = op->d.arrayexpr.elemtype;
	int			nelems = op->d.arrayexpr.nelems;
	int			ndims = 0;
	int			dims[MAXDIM];
	int			lbs[MAXDIM];

	/* Set non-null as default */
	*op->resnull = false;

	if (!op->d.arrayexpr.multidims)
	{
		/* Elements are presumably of scalar type */
		Datum	   *dvalues = op->d.arrayexpr.elemvalues;
		bool	   *dnulls = op->d.arrayexpr.elemnulls;

		/* setup for 1-D array of the given length */
		ndims = 1;
		dims[0] = nelems;
		lbs[0] = 1;

		result = construct_md_array(dvalues, dnulls, ndims, dims, lbs,
									element_type,
									op->d.arrayexpr.elemlength,
									op->d.arrayexpr.elembyval,
									op->d.arrayexpr.elemalign);
	}
	else
	{
		/* Must be nested array expressions */
		int			nbytes = 0;
		int			nitems = 0;
		int			outer_nelems = 0;
		int			elem_ndims = 0;
		int		   *elem_dims = NULL;
		int		   *elem_lbs = NULL;
		bool		firstone = true;
		bool		havenulls = false;
		bool		haveempty = false;
		char	  **subdata;
		bits8	  **subbitmaps;
		int		   *subbytes;
		int		   *subnitems;
		int32		dataoffset;
		char	   *dat;
		int			iitem;

		subdata = (char **) palloc(nelems * sizeof(char *));
		subbitmaps = (bits8 **) palloc(nelems * sizeof(bits8 *));
		subbytes = (int *) palloc(nelems * sizeof(int));
		subnitems = (int *) palloc(nelems * sizeof(int));

		/* loop through and get data area from each element */
		for (int elemoff = 0; elemoff < nelems; elemoff++)
		{