Re: use a variable name for an insert in a trigger for an audit

On 9dic, 2010, at 04:40 , Raimon Fernandez wrote:

> Hello,
>
> I have to audit all the changes for all rows of one database.
>
> I have a trigger that executes BEFORE any update or delete, and simply copy the row (INSERT INTO) into the replicated table.
>
> For example, every table has the same name plus '_audit' at the end and belongs to the schema audit:
>
> table public.persons => audit.persons_audit
>
> I don't want to create specific triggers/functions for every table, so I want to modify the table_name in the INSERT INTO, using the TG_TABLE_NAME, but I can't make it working.
>
> Also I can't see a working solution in the archive, and some examples are quite messy to do, so maybe I have to rethink how I'm doing thinks or just create a specific trigger for each table.
>
> Here is my function, and I'm only testing now the INSERT:
>
> ...
> DECLARE
> tableRemote varchar;
> BEGIN
>
> IF TG_TABLE_NAME = 'assentaments' THEN
> tableRemote:='audit.'||TG_TABLE_NAME||'_audit';
> END IF;
>
> --
> -- Create a row in table_audit to reflect the operation performed on emp,
> -- make use of the special variable TG_OP to work out the operation.
> --
>
> IF (TG_OP = 'DELETE') THEN
> EXECUTE 'INSERT INTO audit.assentaments_audit SELECT CURRVAL(''audit_id_seq''),5, OLD.*';
> RETURN OLD;
> ELSIF (TG_OP = 'UPDATE') THEN
> INSERT INTO tableRemote SELECT CURRVAL('audit.audit_id_seq'),3,OLD.*;
> RETURN OLD;
> END IF;
> RETURN NULL; -- result is ignored since this is an AFTER trigger
> END;
> ...
>
> thanks,
>
> regards,
>

finally I've moved all the audit tables to a new schema called audit, and the tables being audited have now the same name as the 'master' tables.

In the trigger function I want to change the default schema to audit to use the same tablename, but it seems that I can't change the schema in the function.

Also, as now the audit tables belong to the audit schema and have the same name, I'm trying to use just the TG_TABLE_NAME as this:

INSERT INTO TG_TABLE_NAME SELECT CURRVAL('audit.audit_id_seq'),3,OLD.*;

but also isn't allowed ...

I have to specify always a fixed value for the INSERT INTO myTable to work ?

If I use:

INSERT INTO assentaments SELECT CURRVAL('audit.audit_id_seq'),3,OLD.*;

this works perfectly, as the trigger function belongs to the audit schema, I can use the same table name, but I can't use the TG_TABLE_NAME, and I have only two options:

- use the same triggger function with IF ELSEIF to test wich table invoked the trigger function
- or just write a different trigger function for each table.

what are the best options ?

thanks for your guide!

regards,

r.

also I'm trying to change the default schema