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Home -> Community -> Usenet -> c.d.o.server -> Re: Optimizer problem?
On Thu, 09 Oct 1997 19:37:46 +0200, Norbert Ferstl <ferstl_at_netway.at> wrote:
>Phil Tsao wrote:
>>
>> Hi,
>>
>> I was wondering if any one has experienced the same problem.
>> I have a loop to add 10,000 rows to a table one by one then another loop
>>
>> to delete each row one by one. After doing so a few times, the
>> "select count(*) from table" starts doing table scan ( and physical
>> read)
[snip]
>> philt_at_technologist.com
>
>
>
>If you use an index as discribed in other reply(s)
>it's OK.
>BUT your first full table scan WILL be time-consumting because of the
>delayed block-ceanout, witch means to mark the emptied block
>as empty in the second access transaction.
>So assume to make a full-table scan after a large delete.
>
Note: As of Oracle Server release 7.3, performing a SELECT COUNT (*) no longer does a block cleanout.
>
Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Bethesda MD
http://govt.us.oracle.com/ -- downloadable utilities
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