使用游标在python中调用存储过程

Question

The data in the redshift will be changed whenever there is new table schema added in the database. I am trying to fetch all the table_schema names in the information_schema.tables.

So I have created a stored procedure that returns a distinct table_schema name using cursor method. Now i would like it to call in my project using python.

Stored Procedure:

CREATE OR REPLACE PROCEDURE get_dist_schema(rsout INOUT refcursor)
AS $$
BEGIN 
  OPEN rsout FOR SELECT DISTINCT table_schema FROM information_schema.tables;
END;
$$ LANGUAGE plpgsql;

//this is used in the database to fetch all rows
BEGIN;
CALL get_dist_schema('sname');
FETCH ALL FROM sname;

commit;

python.py

def call_dist_name(sname):
    conn = None

    try:
        params = config()
        conn = psycopg2.connect(**params)
        cur = conn.cursor()

        cur.execute('CALL get_dist_schema(%s)' % sname)

        conn.commit()
        result = cur.fetchall()
        for row in result:
                print(row[0])
        cur.close()



    except(Exception, psycopg2.DatabaseError) as error:
        print(error)

    finally:
        if conn is not None:
            conn.close()    


if __name__ == '__main__':
    call_dist_name('sname')

Error: column "sname" does not exist.

How do I get the display result set in the stored procedure in my project?

Answer 1

I think the issue is that the value ( sname ) being passed to the stored procedure isn't being quoted:

cur.execute('CALL get_dist_schema(%s)' % sname)

With substitution of the variable, it will result in:

cur.execute('CALL get_dist_schema(sname)')

whereas it should be:

cur.execute("CALL get_dist_schema('sname')")

Therefore, change the line to:

cur.execute("CALL get_dist_schema('%s')" % sname)