zhangjinyu <beijing_pg@163.com> writes:
> The DDL query(alter ...set data type ) rewrites all tuples with new
> transaction xid, so if the transaction isolation level is repeatable read,
> that will cause wrong result.
Yes. This is unlikely to change, but we ought to document it.
I see that we have documentation warning about this sort of effect in the
TRUNCATE reference page, but not in ALTER TABLE's. Rather than
copy-and-paste that, ISTM it'd be better to move the warning to somewhere
in mvcc.sgml.
regards, tom lane