zhangjinyu <beijing...@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


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