Problem while logging primary key of updated field.

Hi,

I want to log the primary key of a table whenever a new row is inserted.
To achieve this, I created the following function as trigger on update.
However I get the following error on inserts:

ERROR: NEW used in non-rule query

Here is my function:
The first select inside the function body gives me the name of the primary
key field.

-----------------------------------------------------------------------
create function log_insert() returns opaque as '
declare
currtime timestamp := ''now'';
pkeyname name;
query text;
begin
select into pkeyname c.attname
from pg_class a,
pg_index b,
pg_attribute c
where
a.relname = TG_RELNAME and
a.oid = b.indrelid and
a.oid = c.attrelid and
b.indkey[0] = c.attnum and
b.indisprimary=''t'';
query := ''insert into logtable (pkvalue, tablename, time)
values (NEW.'' ||
quote_ident(pkeyname) ||
'', '' ||
quote_ident(TG_RELNAME) ||
'', '' ||
quote_ident(currtime) ||
'');'';
execute query;
return null;
end;
' language 'plpgsql';
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I would be extremely grateful for any help. I might add that when I print
the dynamic query with a "raise notice" the query looks fine.

Thanks in advance

Gurunandan