Re: creating audit tables

Hmm. You have an audit_ table for each table that is audited. I chose
to have one big ugly audit table for all audited tables. I wonder which
is more flexible/useful.

Right off the bat I can see that if you add or rename a column you would
need to add or rename a column in your audit_ table and re-produce the
functions/triggers. I guess dropped columns would just show nulls from
then on. Column name changes lose history of the field name too.

Queries are a PITA with my schema, I can see where they would be easier
with yours. I can imagine a pivot function that would make life easier
with my schema though.

Any thoughts would be appreciated, I might take a hack at this in C.

- Ian

>>> Scott Cain <cain(at)cshl(dot)org> 10/15/04 8:27 AM >>>
Hi Tom,

You are probably right that the performance will become an issue. I do
have a working solution using plpgsql, though, so I will at least try it
out for a while.

For anyone who is interested, I created a template file (using the perl
module Template.pm syntax) that works with the perl module
SQL::Translator to examine my ddl file and create from it the audit
tables and the functions and triggers to make them work. The template
file copied below, and SQL::Translator is available from CPAN and from
http://sqlfairy.sourceforge.net/ .

Thanks,
Scott

----------------------------------------------
--audit tables generated from
-- % sqlt -f PostgreSQL -t TTSchema --template add-audits.tmpl
nofuncs.sql > \
-- audits.sql



[% FOREACH table IN schema.get_tables %]
DROP TABLE audit_[% table.name %];
CREATE TABLE audit_[% table.name %] ( [% FOREACH field IN
table.get_fields %]
[% field.name %] [% IF field.data_type == 'serial'; 'int'; ELSE;
field.data_type; END %][% IF field.size AND (field.data_type == 'char'
OR field.data_type == 'varchar') %]([% field.size.join(', ') %])[% END
%], [% END %]
transaction_date timestamp not null default now(),
transaction_type char(1) not null
);
GRANT ALL on audit_[% table.name %] to PUBLIC;



CREATE OR REPLACE FUNCTION audit_update_delete_[% table.name %]()
RETURNS trigger AS
'
DECLARE
[% FOREACH field IN table.get_fields %][% field.name %]_var [% IF
field.data_type == 'serial'; 'int'; ELSE; field.data_type; END %][% IF
field.size AND (field.data_type == 'char' OR field.data_type ==
'varchar') %]([% field.size.join(', ') %])[% END %];
[% END %]
transaction_type_var char;
BEGIN
[% FOREACH field IN table.get_fields %][% field.name %]_var =
OLD.[% field.name %];
[% END %]
IF TG_OP = ''DELETE'' THEN
transaction_type_var = ''D'';
ELSE
transaction_type_var = ''U'';
END IF;



INSERT INTO audit_[% table.name %] ( [% FOREACH field IN
table.get_fields %]
[% field.name %], [% END %]
transaction_type
) VALUES ( [% FOREACH field IN table.get_fields %]
[% field.name %]_var, [% END %]
transaction_type_var
);



IF TG_OP = ''DELETE'' THEN
return null;
ELSE
return NEW;
END IF;
END
'
LANGUAGE plpgsql;



DROP TRIGGER [% table.name %]_audit_ud ON [% table.name %];
CREATE TRIGGER [% table.name %]_audit_ud
BEFORE UPDATE OR DELETE ON [% table.name %]
FOR EACH ROW
EXECUTE PROCEDURE audit_update_delete_[% table.name %] ();



[% END %]

On Fri, 2004-10-15 at 11:02, Tom Lane wrote:
> Scott Cain <cain(at)cshl(dot)org> writes:
> > Heck! So much for feeling close. It is somewhat frustrating to me
that
> > such an obviously useful tool (having and using audit tables) should
be
> > so difficult to implement.
>
> The only really reasonable way to implement this is as a C function
> anyway. I think anything involving a PL language is going to be a
huge
> performance drag, if you intend to put it on essentially every table.
>
> There are some pretty closely related examples in contrib/spi/, though
> I don't see anything that does *exactly* what you want. If you came
up
> with something that does, I think it'd be reasonable to add it to that
> set of examples ...
>
> regards, tom lane
--
------------------------------------------------------------------------
Scott Cain, Ph. D. cain(at)cshl(dot)org
GMOD Coordinator (http://www.gmod.org/) 216-392-3087
Cold Spring Harbor Laboratory