Modelling versioning in Postgres

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

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@protonmail.ch> 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