On 6/11/24 12:20, veem v wrote:
>
>
> On Wed, 12 Jun 2024 at 00:26, hubert depesz lubaczewski
> <depesz@depesz.com <mailto:depesz@depesz.com>> wrote:
>
>
>
> No, I meant building dynamic queries and then EXECUTE-ing, like docs
> show:
> https://www.postgresql.org/docs/current/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN
<https://www.postgresql.org/docs/current/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN>
>
> Best regards,
>
> depesz
>
>
> My apology, if interpreting it wrong way. It doesn't make much
> difference though, but do you mean something like below?
>
> CREATE OR REPLACE FUNCTION log_deletes()
> RETURNS TRIGGER AS $$
> DECLARE
> audit_table_name TEXT;
> audit_query TEXT;
> BEGIN
> IF TG_TABLE_NAME = 'source_table1' THEN
> audit_table_name := 'delete_audit1';
> audit_query := 'INSERT INTO ' || audit_table_name || '
> (record_id, delete_timestamp, col1, col2, col3) VALUES ( $2, $3, $4)';
> EXECUTE audit_query USING OLD.id, OLD.col1, OLD.col2, OLD.col3;
> ELSIF TG_TABLE_NAME = 'source_table2' THEN
> audit_table_name := 'delete_audit2';
> audit_query := 'INSERT INTO ' || audit_table_name || ' ( col4,
> col5, col6) VALUES ( $2, $3, $4)';
> EXECUTE audit_query USING OLD.id, OLD.col4, OLD.col5, OLD.col6;
>
> ELSE
> RAISE EXCEPTION 'Audit table not defined for %', TG_TABLE_NAME;
> END IF;
>
> RETURN OLD;
> END;
> $$ LANGUAGE plpgsql;
I'm guessing depesz meant using TG_TABLE_NAME to pull column information
from:
https://www.postgresql.org/docs/current/catalog-pg-attribute.html
and use that to build the INSERT query. The issue with dynamic or a
fixed SQL is going to be with audit_query, in particular
audit_table_name := 'delete_audit2. If your source tables change, add or
delete columns or column types change, your audit table will need to
change to match.
One possible solution is something I outlined here:
https://aklaver.org/wordpress/2021/12/07/postgres-and-json/
Other folks have done similar things, you can search on
postgresql audit tables using json
for alternatives.
--
Adrian Klaver
adrian.klaver@aklaver.com