| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
 |
 | |||
| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
|
| |||
Home -> Community -> Mailing Lists -> Oracle-L -> RE: Delete followed by Select Count(1) - SLOW
Yes,
It has been known if you delete all records, use a truncate and not delete. Otherwise it will still behave like it is full as it has to touch all the extents.
"Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."
Christopher R. Spence
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275
Fuelspot
73 Princeton Street
North, Chelmsford 01863
-----Original Message-----
Sent: Thursday, August 16, 2001 5:33 PM
To: Multiple recipients of list ORACLE-L
I have a user that deleted all of the rows in a table (i.e. 100,000), waited for it to complete, and then ran a SELECT COUNT(1) FROM <table>. It took a few minutes for '0 rows' to be returned to the prompt. The table has ~60 extents (128k ea.). Granted, the number of extents is excessive but it's a development instance and this table is an exception.
Is Oracle scanning through all of the blocks, since the space wasn't released, and this is the cause of the latency?
The curious thing is that I told this user to use TRUNCATE instead and we talked about using the drop/reuse storage clauses. He performed a TRUNCATE...REUSE STORAGE and the same select and it was night and day in terms of performance. If the allocated space isn't being released in this case also, why is there such a performance difference between the two?
-w
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Liststo: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Liststo: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Thu Aug 16 2001 - 15:42:33 CDT
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
 |
 |