Re: Storing original rows before update or delete

On 4 November 2011 10:20, Miroslav Šimulčík <simulcik(dot)miro(at)gmail(dot)com> wrote:

> Hi.
>
> I'm working on transactiontime temporal support for postgresql 9.0.4. Each
> original table with transactiontime support has associated history table,
> where original row is stored before each update or delete operation on it.
> Both original and history tables have internal timestamp columns for
> storing the period of validity of row versions. History tables are internal
> and I want to restrict any DML operation on it, so nobody can change
> history of operations made on original table. Problem is, that I don't know
> where to implement the mechanism for storing original rows to history
> tables. Rewrite rules are not suitable, because they are not working with
> inheritance and I can't use triggers, because inserts to history tables are
> restricted. Can you point me to place in postgresql backend where can i
> implement this and maybe give me some hints about how to do it correctly?
>
> Thank you.
>
> Best regards
> Miroslav Simulcik
>

Hi,
use triggers with security definer so the owner of the triggers and the
history table can insert into it, but normal user cannot - this user only
is able to change data in original table, and triggers will copy the data,
but will be executed using the first user credentials.
http://www.postgresql.org/docs/9.0/interactive/sql-createfunction.html

On the other hand: superuser always can delete data from a table, so you
cannot stop him from doing that.

regards
Szymon