Which sorting algorithm Oracle use?

Hi ,
May i know which sorting algorithm oracle use ?
Because when i am using order by with an sorted or unsorted data it is taking same time.
Thanks in advance

Pradeep Dewani wrote:
Hi ,
But i want to know that whether oracle consider sorted and unsorted data in same way or not ?
Please help if any body know because i cant decrease number of rows but i can sorted them in a temp table .Pradeep,
a SORT is usually an additional operation that can be quite costly depending on the amount of data to sort and the available memory for sorting. It would show up in the execution plan as SORT operation.
Note that the optimizer can take various shortcuts to minimize the impact of a sort operation. If you e.g. use a "top-N" query properly, it can take advantage of a "SORT ORDER BY STOPKEY" operation that only keeps the top N rows sorted in memory.
If you have suitable indexes, the optimizer might also come to the conclusion that a SORT operation can be eliminated by traversing an index in the requested order, so you could have a query that uses an ORDER BY but the execution plan doesn't show any explicit SORT operations.
So to answer your question: Oracle doesn't consider sorted and unsorted data in the same way. Sorting is an additional operation that needs to be handled somehow.
If you have a query that takes the same time whether sorted or not the execution time is probably driven by other factors and the SORT operation is negligible in terms of performance.
But there are other scenarios possible where a SORT operation takes significant time and influences the execution time. SORTs can also lead to overall changes in the execution plan that are not directly related to the SORT operation.
Regards,
Randolf
Oracle related stuff blog:
http://oracle-randolf.blogspot.com/
SQLTools++ for Oracle (Open source Oracle GUI for Windows):
http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/

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