Function array_cmp

src/backend/utils/adt/arrayfuncs.c:3875–4039

* array_cmp() * Internal comparison function for arrays. * * Returns -1, 0 or 1 */

 * Returns -1, 0 or 1
 */
static int
array_cmp(FunctionCallInfo fcinfo)
{
	LOCAL_FCINFO(locfcinfo, 2);
	AnyArrayType *array1 = PG_GETARG_ANY_ARRAY_P(0);
	AnyArrayType *array2 = PG_GETARG_ANY_ARRAY_P(1);
	Oid			collation = PG_GET_COLLATION();
	int			ndims1 = AARR_NDIM(array1);
	int			ndims2 = AARR_NDIM(array2);
	int		   *dims1 = AARR_DIMS(array1);
	int		   *dims2 = AARR_DIMS(array2);
	int			nitems1 = ArrayGetNItems(ndims1, dims1);
	int			nitems2 = ArrayGetNItems(ndims2, dims2);
	Oid			element_type = AARR_ELEMTYPE(array1);
	int			result = 0;
	TypeCacheEntry *typentry;
	int			typlen;
	bool		typbyval;
	char		typalign;
	int			min_nitems;
	array_iter	it1;
	array_iter	it2;
	int			i;

	if (element_type != AARR_ELEMTYPE(array2))
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("cannot compare arrays of different element types")));

	/*
	 * We arrange to look up the comparison function only once per series of
	 * calls, assuming the element type doesn't change underneath us. The
	 * typcache is used so that we have no memory leakage when being used as
	 * an index support function.
	 */
	typentry = (TypeCacheEntry *) fcinfo->flinfo->fn_extra;
	if (typentry == NULL ||
		typentry->type_id != element_type)
	{
		typentry = lookup_type_cache(element_type,
									 TYPECACHE_CMP_PROC_FINFO);
		if (!OidIsValid(typentry->cmp_proc_finfo.fn_oid))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_FUNCTION),
					 errmsg("could not identify a comparison function for type %s",
							format_type_be(element_type))));
		fcinfo->flinfo->fn_extra = (void *) typentry;
	}
	typlen = typentry->typlen;
	typbyval = typentry->typbyval;
	typalign = typentry->typalign;

	/*
	 * apply the operator to each pair of array elements.
	 */
	InitFunctionCallInfoData(*locfcinfo, &typentry->cmp_proc_finfo, 2,
							 collation, NULL, NULL);