Full table scan on query using primary key?
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Thread: Full table scan on query using primary key?

  1. #1
    Join Date
    Nov 2000
    Location
    Pittsburgh, PA
    Posts
    4,004

    Angry Full table scan on query using primary key?

    I am using Oracle 9.2.0.6 on Windows 2000. I have the following query which was generated from Java. When I try to get an explain plan it is telling me that it is doing a full table scan on uln, even though tpfdd_runid_uln is the primary key. If I hint the index, the cost goes way up but the response time is infinitely faster. Can anyone explain why this is? I enclosed the files, they are html files saved with a .txt extension so that I could upload them.

    Code:
      SELECT uln_syn.poe_ald_cal AS grp0, SUM ( uln_syn.sumoftotal_stons ) tot0
        FROM uln_syn
       WHERE EXISTS (
                SELECT ca_keys.comp_key
                  FROM ca_keys
                 WHERE ca_keys.comp_id = '0x080e00000107235e9e7f0a1428098124'
    					AND uln_syn.tpfdd_runid_uln = ca_keys.comp_key)
      GROUP BY uln_syn.poe_ald_cal;
    Attached Files Attached Files
    this space intentionally left blank

  2. #2
    Join Date
    Aug 2002
    Location
    Colorado Springs
    Posts
    5,253
    Your query will ful scan the uln_syn table and test the EXISTS condition for each row. Try this instead:
    Code:
    SELECT uln_syn.poe_ald_cal AS grp0, SUM ( uln_syn.sumoftotal_stons ) tot0
        FROM uln_syn
       WHERE tpfdd_runid_uln = (
                SELECT ca_keys.comp_key
                  FROM ca_keys
                 WHERE ca_keys.comp_id = '0x080e00000107235e9e7f0a1428098124')
      GROUP BY uln_syn.poe_ald_cal;
    David Aldridge,
    "The Oracle Sponge"

    Senior Manager, Business Intelligence Development
    XM Satellite Radio
    Washington, DC

    Oracle ACE

  3. #3
    Join Date
    Nov 2000
    Location
    Pittsburgh, PA
    Posts
    4,004
    Quote Originally Posted by slimdave
    Your query will ful scan the uln_syn table and test the EXISTS condition for each row. Try this instead:
    I had to add where rownum < 2 so that I only got back one row, but it works great. Thanks Dave!!!!!!!!

    Code:
    SELECT uln_syn.poe_ald_cal grp0, SUM ( uln_syn.sumoftotal_stons ) tot0
      FROM uln_syn
     WHERE tpfdd_runid_uln =
           ( SELECT ca_keys.comp_key
               FROM ca_keys
              WHERE ca_keys.comp_id = '0x080e0000010728e3ba1dc046fe878335'
                AND ROWNUM < 2 )
     GROUP BY uln_syn.poe_ald_cal;
    this space intentionally left blank

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