RE: mystery cartesian join

From: Khedr, Waleed <Waleed.Khedr_at_FMR.COM>
Date: Wed, 16 Jan 2002 11:11:09 -0800
Message-ID: <F001.003F1AF0.20020116104739@fatcity.com>

This may be a STAR schema execution plan where Oracle joins dimensions and use Nested loop + index to join it to the fact.

Some times it's very efficient but if you do not like it I think there is a parameter in init.ora that disables it.

Regards,

Waleed

-----Original Message-----
Sent: Wednesday, January 16, 2002 12:10 PM To: Multiple recipients of list ORACLE-L

Hello gurus,

I have a query which seems to have a mystery cartesian join in it and I can't seem to locate it. I would definitely appreciate some help if possible. My view doesn't have a join associated with it and it appears that I have the correct number of joins for the number of tables I am selecting from. I have also recently rebuilt my indexes and analyzed all tables. One other point is that I am joining across schemas by way of synonyms. The si_monitor table resides in a separate schema. Hmmmm?

Here is my query:

SELECT vslfl.error_type_id error_type_id,

        vslfl.interface_id,
        sm.error_check,
       86400 * (sysdate - sm.error_time) err_secs,
        slt.warn,
        slt.shortname
    FROM v_si_last_faq_log vslfl,
        si_monitor sm,
        sm_log_type slt

    WHERE vslfl.interface_id = sm.interface_id     AND vslfl.error_type_id = slt.error_type_id     AND vslfl.interface_id = 1
/

Here is the output from the tkprof:

SELECT vslfl.error_type_id error_type_id,

        vslfl.interface_id,
        sm.error_check,
       :"SYS_B_0" * (sysdate - sm.error_time) err_secs,
        slt.warn,
        slt.shortname
    FROM v_si_last_faq_log vslfl,
        si_monitor sm,
        sm_log_type slt

    WHERE vslfl.interface_id = sm.interface_id     AND vslfl.error_type_id = slt.error_type_id     AND vslfl.interface_id = :"SYS_B_1"

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ----------

---

Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 0.71 1.68 3114 3540 4 1
------- ------ -------- ---------- ---------- ---------- ----------

---

total 4 0.71 1.68 3114 3540 4 1

Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 18 (SITEMON)

Rows Row Source Operation

-------  ---------------------------------------------------
      1  NESTED LOOPS
      2   MERGE JOIN CARTESIAN
      2    VIEW V_SI_LAST_FAQ_LOG
      2     SORT ORDER BY
      1      TABLE ACCESS BY INDEX ROWID SI_LOG
   3629       INDEX RANGE SCAN (object id 3281)
      2    SORT JOIN
      1     TABLE ACCESS FULL SI_MONITOR
      1   TABLE ACCESS BY INDEX ROWID SM_LOG_TYPE
      2    INDEX UNIQUE SCAN (object id 3318)


Rows     Execution Plan
-------  ---------------------------------------------------
      0  SELECT STATEMENT   GOAL: CHOOSE
      1   NESTED LOOPS
      2    MERGE JOIN (CARTESIAN)
      2     VIEW OF 'V_SI_LAST_FAQ_LOG'
      2      SORT (ORDER BY)
      1       TABLE ACCESS   GOAL: ANALYZED (BY INDEX ROWID) OF
                  'SI_LOG'
   3629        INDEX   GOAL: ANALYZED (RANGE SCAN) OF
                   'SI_LOG_INT_IDX' (NON-UNIQUE)
      2     SORT (JOIN)
      1      TABLE ACCESS   GOAL: ANALYZED (FULL) OF 'SI_MONITOR'
      1    TABLE ACCESS   GOAL: ANALYZED (BY INDEX ROWID) OF
               'SM_LOG_TYPE'
      2     INDEX   GOAL: ANALYZED (UNIQUE SCAN) OF 'SM_LOG_TYPE_PK'
                (UNIQUE)

Here is the syntax from my view (v_si_last_faq_log):

SELECT error_id last_error_id,

        interface_id,
        error_type_id,
        ewhen,
        request_time

FROM si_log
WHERE last_faq_log = 'Y'
ORDER BY error_id
/

Any help would be appreciated.

Thanks in Advance

ReedK

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Received on Wed Jan 16 2002 - 13:11:09 CST