Re: unlimited undo/journaling

> > so what i want is basically an unlimited undo or journalling feature
> > for more or less every field.
> >
> > the idea should be to save the data-difference in some journalling
> > table, but i'm not sure how this could be done properly. maybe
> > somebody with some experience can help me here ?
>
> Perhaps the simplest system is to have two tables: address
> and arc_address.
> Use "before" triggers on address to copy the old data into
> arc_address and
> stamp it with a version number/timestamp.
>
> I've done something similar to this using a sequence to
> generate unique
> version numbers for me.

I have too, but not using a sequence, but instead another table for
version numbers:
Create table trans_version (trans_id int4, version int4);

Copying the current data into the archive table is quick and efficient
with this method:
Create table mytrans(trans_id int4, date_modified timestamp, ...);
Create table arch_mytrans(version int4, trans_id int4, date_modified
timestamp, ...);

Then, when modifying a document:
Begin;
Insert into arch_mytrans select <new version #>, * from mytrans where
transi_d = <trans id>;
Update trans_version set version=<new version #> where trans_id = <trans
id>;
Commit;

This allows you to add more fields to your tables without messing with
your versioning code.

Glen Parker
glenebob(at)nwlink(dot)com