Postgres - Return multiple columns in function - postgresql

Question

At the company that I work at it is common to store some metadata with each table row such as the time at which the row has been created and by whom (in reality, there is more metadata, but I will just stick to these two for simplicity).
The columns are "creationTimestamp" and "createdBy". Explicitly selecting each of the columns is quite tedious and I would prefer a soluition where I just have to tell the SQL that it should kindly select all of the metadata columns at once.
Standard-SQL (with explicit select) looks like this:
SELECT "foo", "creationDate", "createdBy" from "bar";
and I would like a solution that looks something like this:
SELECT "foo", select_default_meta() from "bar";
Also please note that a simple select * from "bar" is not a viable solution!

Answer 1

demo
BEGIN;
CREATE temp TABLE bar (
col1 text,
col2 int,
col3 date,
col4 timestamptz,
creationDate date,
created_by text,
last_update timestamptz,
last_updated_by text
);
CREATE temp VIEW bar_meta AS
SELECT
creationDate,
created_by,
last_update,
last_updated_by
FROM
bar;
COMMIT;
CREATE OR REPLACE FUNCTION bar_metas (IN text)
RETURNS TABLE (
creationDate date,
created_by text,
last_update timestamptz,
last_updated_by text
)
AS $a$
BEGIN
RAISE NOTICE '%', quote_ident($1);
RETURN query
SELECT
creationDate,
created_by,
last_update,
last_updated_by
FROM
quote_ident($1);
END;
$a$
LANGUAGE plpgsql;
expand meta columns from function.
SELECT
*
FROM (
SELECT
col1,
col2,
col3
FROM
bar) c,
LATERAL bar_metas ('bar');
directly use view
SELECT
col1,
col2,
col3,
b.*
FROM
bar
CROSS JOIN bar_meta b;
demo both view and function. view is much easier. But, the view access control is kind of tricky.
SELECT "foo", select_default_meta() from "bar";. select_default_meta() will only generate one column. Further explanation: https://www.postgresql.org/docs/current/xfunc-sql.html#XFUNC-SQL-COMPOSITE-FUNCTIONS
To make function expand all the columns, then you need to somehow use pattern. select * from function(); This is the reason why need use lateral.