Re: How to lose transaction history (xmin values, WAL, etc.)?

Alvaro Herrera wrote:
> Excerpts from Richard Walker's message of jue may 20 02:19:17 -0400 2010:
>
>> (a) (ii) It seems a breach is possible via the xmin values.
>> In that case, what about doing updates inside a transaction
>> that does a trivial update of all rows, e.g.:
>>    begin transaction;
>>    update mytable ....; -- change one row
>>    update mytable set id=id; -- change all rows
>>    commit;
>> So now all rows have the same xmin values.
>> Does this work?  Performance is not so good, is it?
>> Is there a better way?
>
> The easiest way to do this is probably VACUUM FREEZE.

Thank you very much - that works perfectly to solve
case (a) (ii).

It turns out it doesn't solve my case (b)
in which the hacker can read the raw files.

After a little bit of experimenting I found
that VACUUM FREEZE followed by CLUSTER gives
me a fresh raw table file with no transaction
history.  Now all I need is a way to deal
with the WAL . . .


--
Richard Walker
Software Improvements Pty Ltd
Phone:  +61 2 6273 2055
Fax:  +61 2 6273 2082