Re: Nested loop very slow

From: <nlzanen1_at_EY.NL>
Date: Thu, 23 Aug 2001 04:43:44 -0700
Message-ID: <F001.00374DBB.20010823044531@fatcity.com>

Hi,

AFAIK
It does the index range scane 32000 times, whereas the hash join reads both tables just once.

Jack

                                                                                       
                          
                    "Daemen,                                                           
                          
                    Remco"               To:     Multiple recipients of list ORACLE-L 
<ORACLE-L_at_fatcity.com>     
                    <R.Daemen_at_face       cc:     (bcc: Jack van 
Zanen/nlzanen1/External/MEY/NL)                  
                    nt.nl>               Subject:     Nested loop very slow            
                          
                    Sent by:                                                           
                          
                    root_at_fatcity.c                                                     
                          
                    om                                                                 
                          
                                                                                       
                          
                                                                                       
                          
                    23-08-2001                                                         
                          
                    13:56                                                              
                          
                    Please respond                                                     
                          
                    to ORACLE-L

Hi,

I'm joining a table with 32000 rows with a very large table (3 Gb), resulting in 97000 records. When I execute the query without hints, it uses a full table scan and a hash join, and returns a result in 4 minutes. When I
use a hint forcing a nested loop (and part of an index (range scan)), the query takes 14 minutes to complete. The question is: why does a join between
an inner table with 32000 records and a large table using a range scan on an
index take so long ? I would expect Oracle to give a result within seconds, a few minutes tops !

The table has very few chained rows and I've rebuilt the index recently. RDBMS is 8.1.6. Index and data are divided over many different disks.

Any suggestions ? Except kicking the server ?

Remco

--

Please see the official ORACLE-L FAQ: http://www.orafaq.com
--

Author: Daemen, Remco
INET: R.Daemen_at_facent.nl

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists


--------------------------------------------------------------------

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).

De informatie verzonden in dit e-mailbericht is vertrouwelijk en is uitsluitend bestemd voor de geadresseerde. Openbaarmaking, vermenigvuldiging, verspreiding en/of verstrekking van deze informatie aan derden is, behoudens voorafgaande schriftelijke toestemming van Ernst & Young, niet toegestaan. Ernst & Young staat niet in voor de juiste en volledige overbrenging van de inhoud van een verzonden e-mailbericht, noch voor tijdige ontvangst daarvan. Ernst & Young kan niet garanderen dat een verzonden e-mailbericht vrij is van virussen, noch dat e-mailberichten worden overgebracht zonder inbreuk of tussenkomst van onbevoegde derden.

Indien bovenstaand e-mailbericht niet aan u is gericht, verzoeken wij u vriendelijk doch dringend het e-mailbericht te retourneren aan de verzender en het origineel en eventuele kopieën te verwijderen en te vernietigen.

Ernst & Young hanteert bij de uitoefening van haar werkzaamheden algemene voorwaarden, waarin een beperking van aansprakelijkheid is opgenomen. De algemene voorwaarden worden u op verzoek kosteloos toegezonden.

The information contained in this communication is confidential and is intended solely for the use of the individual or entity to whom it is addressed. You should not copy, disclose or distribute this communication without the authority of Ernst & Young. Ernst & Young is neither liable for the proper and complete transmission of the information contained in this communication nor for any delay in its receipt. Ernst & Young does not guarantee that the integrity of this communication has been maintained nor that the communication is free of viruses, interceptions or interference.

If you are not the intended recipient of this communication please return the communication to the sender and delete and destroy all copies.

In carrying out its engagements, Ernst & Young applies general terms and conditions, which contain a clause that limits its liability. A copy of these terms and conditions is available on request free of charge.

--

Please see the official ORACLE-L FAQ: http://www.orafaq.com
--

Author:
INET: nlzanen1_at_EY.NL

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists


--------------------------------------------------------------------

To REMOVE yourself from this mailing list, send an E-Mail message