Tyler Muth’s Blog

Technology with a focus on Oracle, Application Express and Linux

Exadata Smart Scan – Just The Columns I Want

Posted by Tyler Muth on June 23, 2010

In my last post I talked about the Smart Scan component of cell offload processing.  I showed how much network traffic this can save between storage and the Database. That savings comes from the fact that the storage filters the results down just the rows and columns you asked for.  This is just a quick post to demonstrate the difference in bytes shipped across the wire between selecting one column and selecting all columns.

-- query v$mystat

select *
 from all_objs
 where object_type = 'TABLE'
 and object_name like '%RESOURCE%';

-- query v$mystat

select object_name
 from all_objs
 where object_type = 'TABLE'
 and object_name like '%RESOURCE%';

-- query v$mystat

 ALL_COLUMNS_MB    ONE_COLUMN_MB      FACTOR_OF_IMPROVEMENT
------------------ ------------------ ---------------------
 5.4               1.8                3.0
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2 Responses to “Exadata Smart Scan – Just The Columns I Want”

  1. Evgeny said

    Hi, Tyler!
    I can’t reproduce this example. It seems that if the row is located in several blocks Smart Scan in this case works.
    Regards,
    Evgeny / RuOUG

  2. sex said

    Very good blog ..

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