Tracking DDL and DML changes in Postgresql and different versions of database (advance)

On Wed, May 30, 2018, 11:03 AM Łukasz Jarych <jaryszek@gmail.com> wrote:

Hi Guys,

i am using Access FE and Postgresql BE.
To track DML changes i have history log table wotking like here:

https://www.fontstuff.com/access/acctut21.htm

It is ok but this doesnt solve the problem with trakich DDL changes.

For DDL changes i can use flyway system but how to combine this with my
DML trackinh system?

Do you have any solutions for this?

My boss wants to have possibility to save the current version (state) of
database with DML and DDL changes. And to easily revert and go back to
previous version (rollback all changes).

I do not think so that postgresql has triggers on DDL changes and - this
is the most optimal solution?

Best Wishes,
Luke

Hi Lukasz,

I think by using triggers(for DML-> Insert, Update, Delete, Truncate), you
can achieve this. You can log the entire query which does this change.

And regarding DDL(Create, Alter), you can use concept of event trigger
where the tags like "ddl_command_start","table_rewrite","ddl_command_end"
are available which let's you to get all the ddl changes into a table.

So by using above things, I hope you can achieve. Feel free to ask if
anything is unclear.

Regards,
Pavan

---------- Forwarded message ----------
From: Łukasz Jarych <jaryszek@gmail.com>
Date: 2018-05-30 9:35 GMT+02:00
Subject: Re: Tracking DDL and DML changes in Postgresql and different
versions of database (advance)
To: Pavan Teja <pavan.postgresdba@gmail.com>

Thank you Pavan,

I have a few questions.

Could you please describe in more details about event triggers? Maybe some
examples how to start with this?

And regarding changes, how to create exact state of database and give the
version for it?

Best,
Luke

2018-05-30 8:11 GMT+02:00 Pavan Teja <pavan.postgresdba@gmail.com>:

Hi Luke,

Thank you Pavan,

I have a few questions.

Could you please describe in more details about event triggers? Maybe some

examples how to start with this?

Please refer the below link for more detailed information about "Event
Triggers".

Link: https://www.postgresql.org/docs/10/static/sql-createeventtrigger.html
<https://www.postgresql.org/docs/10/static/sql-createeventtrigger.html&gt;

You can find the below sample procedure along with the event trigger which
executes for every DDL against the database.

--Procedure
CREATE OR REPLACE FUNCTION snitch() RETURNS event_trigger AS $$
BEGIN
RAISE NOTICE 'snitch: % %', tg_event, tg_tag;
END;
$$ LANGUAGE plpgsql;

--Event Trigger
CREATE EVENT TRIGGER snitch ON ddl_command_start EXECUTE PROCEDURE snitch();

If you execute above code you can find that the event trigger snitch raises
a notice message whenever ddl fires on the database. Do let me know if you
face any problem.

And regarding changes, how to create exact state of database and give the

version for it?

Instead of the notice message in the above procedure, you can simple insert
user info, timestamp at the time of ddl command start, actual query, and the
tag name(tg_tag=> whether to determine it is ALTER/CREATE/SECURITY
LABEL/DROP/COMMENT/GRANT or REVOKE).

Please feel free to write up if any queries persists.

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