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select partition table with non partition key condition [message #462718]

Sat, 26 June 2010 01:51

ekopur
Messages: 9
Registered: June 2010
Location: indonesia

Junior Member

I have a table that partitioned into six partitions.
each partitions placed in different table space and every two table space
placed it on a different hardisk

when I will do query select with the non-partition keys condition,
how the search process ?
whether the sequence (scan sequentially from partition 1 to partition 6)
or partition in a hardisk is accessed at the same time with other partition in other hardisk.
( in the image, partition 1,4 accessed at the same time with partition 2,5 and 3,6)

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Re: select partition table with non partition key condition [message #462727 is a reply to message #462718]

Sat, 26 June 2010 03:01

Michel Cadot
Messages: 68650
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

It's more an OS question than an Oracle one. Oracle does not care about real physical implementation, its physical level is the file, its logical level (on which execution plan is built) is the partition.
So if you want to know how it does it on your hard disk then use iostat.

Note that "at the same time" is only relevant if the query is executed in parallel which is not the default mode.

Regards
Michel

[Updated on: Sat, 26 June 2010 03:02]

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Re: select partition table with non partition key condition [message #462738 is a reply to message #462727]

Sat, 26 June 2010 05:17

ekopur
Messages: 9
Registered: June 2010
Location: indonesia

Junior Member

thanx for your replay michel..

so, its mean that acces done with squence from partition 1 to partition 6 ?

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Re: select partition table with non partition key condition [message #462748 is a reply to message #462738]

Sat, 26 June 2010 09:20

Michel Cadot
Messages: 68650
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

No, it means Oracle chooses the way it wants to access the partition, assuming a serialized plan, 1 to 6, or 1 then 2 then 6 then..., or 6 to 1, or odd then even, or... You can make no assumption on the order it will take. The only you can know is that if you parallelize then Oracle will take care of the partition tablespaces to choose an optimal parallelization.

Regards
Michel

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