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From: Kirmo Uusitalo <[email protected]>
To: Samed YILDIRIM <[email protected]>
Cc: [email protected]
Subject: Re: Postgresql long transaction support
Date: Wed, 14 Dec 2022 14:45:47 +0200
Message-ID: <CAH2dGSPW4jVzB1fLwNpZiaL3u1BBsZYACTRzerMy-RnpprMk-A@mail.gmail.com> (raw)
In-Reply-To: <CAAo1mb=fgrfDzP-+5-0i7tDQiWUphZc-Pw5eGNzp7mQ+spOsgA@mail.gmail.com>
References: <CAH2dGSOY+8amTEE12_WkYkPs17=Y0Cy1dbQ+bsvhmBB6cFSRmw@mail.gmail.com>
	<CAAo1mb=fgrfDzP-+5-0i7tDQiWUphZc-Pw5eGNzp7mQ+spOsgA@mail.gmail.com>

Hi Samed,

thanks. The bitemporal tables are somewhat similar except that there is not
a date range to distinguish between versions of objects. One could use this
long transaction feature for comparing the results of different plans of
implementing something - and these could be affecting many objects from the
parent version (or it's parent and so forth).

Similarly as with bitemporal tables the FK constraints are problematic. If
an object is to be deleted in parent version, any created child object of
this in child version cannot be posted to parent version later. That's why
I believe it is best first merge the changes done in parent version to
current version before you are allowed to post.

To solve this in application layer for an existing application is quite
complex and this is why I am looking for a more generic solution within the
database.

On Wed, Dec 14, 2022 at 2:02 PM Samed YILDIRIM <[email protected]> wrote:

> Hi Kirmo,
>
> This is a pretty interesting feature. I'm not sure if I've seen something
> like that before. I recommend you to check the pg_bitemporal[1] project. It
> may be useful for you.
>
> [1]: https://github.com/hettie-d/pg_bitemporal
>
> Best regards.
> Samed YILDIRIM
>
>
> On Wed, 14 Dec 2022 at 13:55, Kirmo Uusitalo <[email protected]>
> wrote:
>
>> Hi,
>>
>> I'm looking for a solution for version managed (or long transaction) data
>> in PostgreSQL (and Oracle).
>>
>> This means database objects having different properties in different
>> versions of the data set. Versions could be organized in tree-like
>> hierarchy (each versios can have subversions). Objects can even be deleted
>> in some of the versions of the data.
>>
>> I am looking for something which would require minimal change in the
>> application logic, like
>>
>>     create table my_obj(id serial primary key,prop_1 text);
>>
>>     insert into my_obj (prop_1) values ('object 1');
>>
>>     insert into my_obj (prop_1) values ('object 2 (to be deleted)');
>>
>>
>> select * from my_obj;
>>
>> 1   object 1
>> 2   object 2 (to be deleted)
>>
>> create version 'xx'; //this functionality i'm looking for
>> switch to version 'xx'; //this functionality i'm looking for
>>
>> select * from my_obj; //same data as in top version as we haven't changed anything yet
>>
>> 1   object 1
>> 2   object 2 (to be deleted)
>>
>> update my_obj set prop_1='updated in version xx' where id = 1;delete from my_obj where id=2;
>>
>> select * from my_obj;
>>
>> 1   'updated in version xx'
>>
>> switch to version 'top'; //let's go back to top version
>>
>> select * from my_obj; //same data as before as we haven't changed posted
>> our changes made in 'xx' yet to top version
>>
>> 1   object 1
>> 2   object 2 (to be deleted)
>>
>> insert into my_obj (prop_1) values ('object 3 (inserted after creation of xx)');
>>
>> switch to version 'xx'; //this functionality i'm looking for
>>
>> merge; //brings changes made in parent 'top' version
>>
>> 1   updated in version xx
>> 3   object 3 (inserted after creation of xx)
>>
>> post; //sends all changes upwards
>>
>> This functionality exists in GE Smallworld spatial database (see
>> https://www.ge.com/content/dam/gepower-new/global/en_US/downloads/gas-new-site/resources/reference/g...)
>> and the use case is quite common (plan some changes in data which will
>> happen in real life in far future, much further away than when current
>> database session ends). Also the conflict management should exist (same
>> object being changed in multiple versions).
>>
>> Does Postgresql have anything like this?
>>
>

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