Function get_sort_group_operators

src/backend/parser/parse_oper.c:191–245

* get_sort_group_operators - get default sorting/grouping operators for type * * We fetch the "<", "=", and ">" operators all at once to reduce lookup * overhead (knowing that most callers will be interested in at least two). * However, a given datatype might have only an "=" operator, if it is * hashable but not sortable. (Other combinations of present and missing * operators shouldn't hap

 * coercion steps.
 */
void
get_sort_group_operators(Oid argtype,
						 bool needLT, bool needEQ, bool needGT,
						 Oid *ltOpr, Oid *eqOpr, Oid *gtOpr,
						 bool *isHashable)
{
	TypeCacheEntry *typentry;
	int			cache_flags;
	Oid			lt_opr;
	Oid			eq_opr;
	Oid			gt_opr;
	bool		hashable;

	/*
	 * Look up the operators using the type cache.
	 *
	 * Note: the search algorithm used by typcache.c ensures that the results
	 * are consistent, ie all from matching opclasses.
	 */
	if (isHashable != NULL)
		cache_flags = TYPECACHE_LT_OPR | TYPECACHE_EQ_OPR | TYPECACHE_GT_OPR |
			TYPECACHE_HASH_PROC;
	else
		cache_flags = TYPECACHE_LT_OPR | TYPECACHE_EQ_OPR | TYPECACHE_GT_OPR;

	typentry = lookup_type_cache(argtype, cache_flags);
	lt_opr = typentry->lt_opr;
	eq_opr = typentry->eq_opr;
	gt_opr = typentry->gt_opr;
	hashable = OidIsValid(typentry->hash_proc);

	/* Report errors if needed */
	if ((needLT && !OidIsValid(lt_opr)) ||
		(needGT && !OidIsValid(gt_opr)))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_FUNCTION),
				 errmsg("could not identify an ordering operator for type %s",
						format_type_be(argtype)),
				 errhint("Use an explicit ordering operator or modify the query.")));
	if (needEQ && !OidIsValid(eq_opr))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_FUNCTION),
				 errmsg("could not identify an equality operator for type %s",
						format_type_be(argtype))));

	/* Return results as needed */
	if (ltOpr)
		*ltOpr = lt_opr;
	if (eqOpr)
		*eqOpr = eq_opr;
	if (gtOpr)
		*gtOpr = gt_opr;
	if (isHashable)
		*isHashable = hashable;
}


/* given operator tuple, return the operator OID */