Function equality_ops_are_compatible

src/backend/utils/cache/lsyscache.c:845–882

* equality_ops_are_compatible * Return true if the two given equality operators have compatible * semantics. * * This is trivially true if they are the same operator. Otherwise, * we look to see if they can be found in the same btree or hash opfamily. * Either finding allows us to assume that they have compatible notions * of equality. (The reason we need to do these pushups is that one

 * be a cross-type operator; for instance int24eq vs int4eq.)
 */
bool
equality_ops_are_compatible(Oid opno1, Oid opno2)
{
	bool		result;
	CatCList   *catlist;
	int			i;

	/* Easy if they're the same operator */
	if (opno1 == opno2)
		return true;

	/*
	 * We search through all the pg_amop entries for opno1.
	 */
	catlist = SearchSysCacheList1(AMOPOPID, ObjectIdGetDatum(opno1));

	result = false;
	for (i = 0; i < catlist->n_members; i++)
	{
		HeapTuple	op_tuple = &catlist->members[i]->tuple;
		Form_pg_amop op_form = (Form_pg_amop) GETSTRUCT(op_tuple);

		/* must be btree or hash */
		if (IsIndexAccessMethod(op_form->amopmethod, BTREE_AM_OID) ||
			IsIndexAccessMethod(op_form->amopmethod, HASH_AM_OID))
		{
			if (op_in_opfamily(opno2, op_form->amopfamily))
			{
				result = true;
				break;
			}
		}
	}

	ReleaseSysCacheList(catlist);

	return result;
}

/*
 * comparison_ops_are_compatible