// it is firebird query
SELECT TRIM(RL.RDB$RELATION_NAME), TRIM(FR.RDB$FIELD_NAME), FS.RDB$FIELD_TYPE, trim(RC.RDB$CONSTRAINT_TYPE)
    FROM RDB$RELATIONS RL
        LEFT OUTER JOIN RDB$RELATION_FIELDS FR ON FR.RDB$RELATION_NAME = RL.RDB$RELATION_NAME
        LEFT OUTER JOIN RDB$FIELDS FS ON FS.RDB$FIELD_NAME = FR.RDB$FIELD_SOURCE
        LEFT OUTER JOIN RDB$INDEX_SEGMENTS ISS ON ISS.RDB$FIELD_NAME = FR.RDB$FIELD_NAME
            INNER JOIN RDB$RELATION_CONSTRAINTS RC ON RC.RDB$CONSTRAINT_NAME = ISS.RDB$INDEX_NAME
            WHERE (RL.RDB$VIEW_BLR IS NULL)
                ORDER BY RL.RDB$RELATION_NAME, FR.RDB$FIELD_NAME

// This query is what have i written.
SELECT TRIM(c.relname) AS table_name, TRIM(a.attname) AS column_name,  a.atttypid AS field_name,  TRIM()
    FROM pg_class c
        LEFT OUTER JOIN pg_attribute a ON c.oid = a.arrrelid
        LEFT OUTER JOIN ... -- no idea
        LEFT OUTER JOIN ... -- -/-
            INNER JOIN ... -- -/-
            WHERE c.relkind = 'r'
                ORDER BY table_name, column_name