In writing a function to test if a column col_name
exists in a table _tbl
, I'd like to extract the table's schema name, which is passed into the function as a regclass
parameter (for security??).
CREATE OR REPLACE FUNCTION column_exists(_tbl regclass, col_name text)
RETURNS bool AS
$func$
SELECT EXISTS (
SELECT 1 FROM information_schema.columns
WHERE table_schema=get_schema($1)
AND table_name=get_table($1)
AND column_name=$2
);
$func$ LANGUAGE sql;
So if the table name is 'staging.my_table'::regclass
, I'd like to get staging
from an imaginary function get_schema
.
Can I just implement this function with e.g. split_part(_tbl::text, '.', 1)
?
In addition, is it guaranteed that the table name _tbl
, when converted to text, will always have a schema name? (i.e. not omitting things such as public.
)
I'm not very familiar with the regclass
type. I searched but couldn't find how to extract the schema name, and just wanted to ask first before re-inventing wheels.