Low performances when querying data dictionary Oracle 11g

Question

Query:
SELECT
ucc_fk.column_name FK_COLUMN_NAME,
ucc_pk.table_name PK_TABLE_NAME,
ucc_pk.column_name PK_COLUMN_NAME
FROM user_constraints uc_fk
INNER JOIN user_cons_columns ucc_fk ON (ucc_fk.constraint_name = uc_fk.constraint_name)
INNER JOIN user_constraints uc_pk ON (uc_pk.constraint_name = uc_fk.r_constraint_name)
INNER JOIN user_cons_columns ucc_pk ON (ucc_pk.constraint_name = uc_fk.r_constraint_name AND ucc_pk.position = ucc_fk.position)
WHERE
uc_fk.constraint_type = 'R' AND
uc_pk.constraint_type = 'P' AND
uc_fk.table_name = 'TABLE_NAME';
works ok on 10g but is very slow on 11g? How to improve performances?

Answer 1

You dont need to join with user_constraints again unless you are trying to avoid references to a unique key.
SELECT ucc_fk.column_name FK_COLUMN_NAME, ucc_pk.table_name PK_TABLE_NAME, ucc_pk.column_name PK_COLUMN_NAME
  FROM user_constraints uc_fk
       JOIN user_cons_columns ucc_fk
          ON (ucc_fk.constraint_name = uc_fk.constraint_name)
       JOIN user_cons_columns ucc_pk
          ON (ucc_pk.constraint_name = uc_fk.r_constraint_name
          AND ucc_pk.position = ucc_fk.position)
WHERE uc_fk.constraint_type = 'R'
   AND uc_fk.table_name = 'TABLE_NAME';As you can see I have removed the join to user_constraints and hence the condition uc_pk.constraint_type = 'P'
The reason being the it is already validated to be in ('P','U') for all r_constraint_names.
G.