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Home -> Community -> Mailing Lists -> Oracle-L -> RE: count(*)
but sequences cannot be decremented by PREVVAL too, what about DELETIONS?!
-----Original Message-----
Sent: Friday, September 20, 2002 8:23 PM
To: Multiple recipients of list ORACLE-L
this is what Oracle invented SEQUENCES for! :)
Tom Mercadante
Oracle Certified Professional
-----Original Message-----
Sent: Friday, September 20, 2002 10:04 AM
To: Multiple recipients of list ORACLE-L
What about having a separate table with a single column and a single row to store only the count, and increment and decrement it using a row trigger on Insert and deletes?
that way select count(*) will be very fast, the only ovehead will of the trigger, which i think should be offset by the performance gained by the select.
Regards
naveen
-----Original Message-----
Sent: Friday, September 20, 2002 6:24 PM
To: Multiple recipients of list ORACLE-L
Rishi,
Do records get deleted from this table? If not, you could simply add an additional column that gets populated by a sequence, add an index on that column, and select max() from that column. Even better, simply query 'select sequence_name,last_number from user_sequences' to get the last value used. You may need to check whether sequence caching makes a difference with this query.
Otherwise, Dennis gave some good advice.
Hope this helps.
Tom Mercadante
Oracle Certified Professional
-----Original Message-----
Sent: Thursday, September 19, 2002 5:04 PM
To: Multiple recipients of list ORACLE-L
Sent: Thursday, September 19, 2002 2:48 PM To: 'ORACLE-L_at_fatcity.com'
Rishi - I've encountered this as well. I think the problem is the fact that you are pounding millions of rows into the table. When you ask for a count, Oracle won't give you an approximate answer, but insists on giving you a precise answer as of the moment you hit return. You are right, your query can actually slow performance. No, to my knowledge Oracle doesn't maintain a record of the number of rows in the table, my guess being that could become a performance bottleneck.
My recommendation would be to ask very precisely what is to be achieved with the count. As you noticed, the count will lag reality by quite awhile. Perhaps the application could maintain the count. I have quite a few batch programs that will display a running counter. If only an approximate count is needed, there may be an alternate method, like looking at how many segments are used and calculating. Just some thoughts.
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com <mailto:dwilliams_at_lifetouch.com>
-----Original Message-----
[mailto:Rishi.Jain_at_VerizonWireless.com]
Sent: Thursday, September 19, 2002 1:28 PM
To: Multiple recipients of list ORACLE-L
Hi Gurus,
In one of our insert intensive application we are inserting around 3-4 million rows / hour. Also this app needs to do a count(*) of the tables every 10 minutes for verifying some application based logic. This is really killing us and it takes a lot of time.
Can you please guide me to a direction ( built in functions or something similar).
Actually this app is being ported from Informix. Informix can somehow keep a trak of the count(*) of a table in its header somewhere.
And yes I have tries count(1) , count(indexed_column) etc.
Thanks In Advance.
R.h
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Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services ---------------------------------------------------------------------To REMOVE yourself from this mailing list, send an E-Mail message to: 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 Fri Sep 20 2002 - 12:04:12 CDT
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