RE: Index access much slower than expected.

Table Numrows 53,424, blocks 5,566

 

Index numrows 53,424 clustering factor 41,357,  blevel 1, distinct keys 28
size 960k

 

Thanks,

Ken

 

From: PD Malik [mailto:pdthedba@xxxxxxxxx] 
Sent: Thursday, May 19, 2011 1:50 PM
To: kennethnaim@xxxxxxxxx; Oracle-L Group
Subject: Re: Index access much slower than expected.

 

Also please post the table.num_blocks, table.num_rows and index clustering
factor.

On Thu, May 19, 2011 at 6:43 PM, Kenneth Naim <kennethnaim@xxxxxxxxx> wrote:

Thanks. I have tried updating stats using compute with/without histograms.
The core of my question is how 2 identical plans with one exception an index
scan of 4% of a small table takes 6 times longer than the same plan with a
full scan of same table. Both the index and table are on the same file
system with identical tablespace parameters, 16k block size auto allocate
extent management, and auto segment space management.

 

Forgot to mention the database is 10.2.0.4

 

From: Allen, Brandon [mailto:Brandon.Allen@xxxxxxxxxxx] 
Sent: Thursday, May 19, 2011 1:21 PM
To: kennethnaim@xxxxxxxxx
Subject: RE: Index access much slower than expected.

 

We'd need a lot more detail on the query, data, and explain plan to tell
exactly what's going on, but if you just want to get the query running
better, I'd suggest first checking to make sure you have your stats
up-to-date on all 4 tables (and their indexes) and try using 100% sample
size if you haven't already.  Also try with and without histograms to see if
it works better one way or the other.

 

Regards,

Brandon 

 

 

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