I have written a function to read certain columns from a table below using a dynamic query:
CREATE OR REPLACE FUNCTION select_cols ()
RETURNS SETOF mytable_name
LANGUAGE plpgsql
AS $$
DECLARE
list_of_columns text;
BEGIN
SELECT
string_agg(trim(cols::text, '()'), ', ') INTO list_of_columns
FROM (
SELECT
'mytable_name.' || column_name
FROM
information_schema.columns
WHERE
table_name = 'mytable_name'
AND column_name LIKE 'rm%_b'
OR column_name LIKE 'rm%_s') AS cols;
RETURN query EXECUTE concat(format('select %s from mytable_name', list_of_columns), ' RETURNING *');
END
$$;
Though when I run
select * from select_cols();
it gives me an error : "cannot open EXECUTE query as cursor". I appreciate if someone can help with this issue
CodePudding user response:
You are not returning a set, but you aggreagte the result set for only one table. So, for only one table you can use:
CREATE OR REPLACE FUNCTION select_colsx ()
RETURNS text
LANGUAGE plpgsql
AS $$
DECLARE
list_of_columns text;
BEGIN
SELECT
'select '||string_agg(trim(cols::text, '()'), ', ') || ' from pg_class RETURNING *'
INTO list_of_columns
FROM (
SELECT
'pg_class.' || column_name
FROM
information_schema.columns
WHERE
table_name = 'pg_class'
AND column_name LIKE 'oid'
OR column_name LIKE 'relacl') AS cols;
RETURN list_of_columns ;
END
$$;
select select_colsx();
CodePudding user response:
RETURN QUERY EXECUTE
was introduced in PostgreSQL 8.4. Upgrade to a less ancient version.