One thing you could consider is a range type for your "versionTS" field instead of a single point in time.
So that would be:
CREATE TABLE objects (
objectID uuid,
versionID uuid,
validRange tsrange,
objectData text,
);
See https://www.postgresql.org/docs/12.5/rangetypes.html for more information.
In particular, you can enforce the obvious business rule, that there is no objectID with overlapping validRanges (as long as you have the btree_gist extension):
CREATE EXTENSION btree_gist;
CREATE TABLE objects (
objectID uuid,
versionID uuid,
validRange tsrange,
objectData text,
EXCLUDE USING GIST(objectID WITH =, validRange WITH &&)
);
On Fri, May 28, 2021 at 8:20 PM Laura Smith <n5d9xq3ti233xiyif2vp@xxxxxxxxxxxxx> wrote:
Hi
I was wondering what the current thinking is on ways to model versioning in Postgres.
The overall premise is that the latest version is the current version unless a rollback has occurred, in which case versions get tracked from the rollback point (forking ?).
My initial naïve starting point is something along the lines of :
create table objects (
objectID uuid,
versionID uuid,
versionTS timestamp
objectData text
);
This obviously creates a fool-proof answer to "latest version is the current version" because its a simple case of an "where objectID=x order by versionTS desc limit 1" query. However it clearly doesn't cover the rollback to prior scenarios.
I then though about adding a simple "versionActive boolean".
But the problem with that is it needs hand-holding somewhere because there can only be one active version and so it would introduce the need for a "active switch" script somewhere that activated the desired version and deactivated the others. It also perhaps is not the right way to deal with tracking of changes post-rollback.
How have others approached the problem ?
N.B. If it makes any difference, I'm dealing with a 12.5 install here, but this could easily be pushed up to 13 if there are benefits.
Thanks for your time.
Laura
