Re: Explain Plan different on TEST and PRODUCTION instance

From: Mohammad Rafiq <rafiq9857_at_hotmail.com>
Date: Mon, 13 Aug 2001 14:34:52 -0700
Message-ID: <F001.0036933F.20010813135603@fatcity.com>

Just for your reading...

MOHAMMAD RAFIQ Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Fri, 03 Aug 2001 15:36:05 -0800

Brijesh,

Even though OPTIMIZER_MODE=RULE, the CBO will be used in the presence of other features (e.g. partitioning, degree of parallelism, etc...).

In this case TEST is getting a better plan because the CBO is being used. You can tell this from several features in the explain plan:

1. Cost = 169 Only the CBO calculates costs.
2. Only the CBO uses hash joins.

The first thing I'd check is the degree of parallelism on the tables AND indexes. In 8.0.5 and 8.1.5 the CBO is used when the indexes have a degree of parallelism
> 1 even if the tables don't (see note: 70008.1).

If you follow the flow chart in Note: 66484.1 "Which Optimizer is Used ?" (looks best if you click on the "fixed font" above the heading for the note) you should find what's causing the CBO to be used on Test.

HTH,

• Anita
  • "Gupta, Brijesh" <Brijesh.Gupta_at_Airliquide.com> wrote:
    > Hi ALL
    >
    > I have a query with was running fast during the
    > test in the test instance
    > and
    > now when moved to production is running very slow.
    > On checking I found that same query is using
    > different explain plan on test
    > and production.
    >
    > Test is exact copy of production database only
    > little older data.
    >
    > Both database running Oracle Application with
    > optimizer mode = RULE .
    > Oracle 8.0.5
    > Platform AIX
    >
    > Can somebody give me a pointer why this is
    > happening.
    >
    > Thanks
    >
    > Here is explain plan from both instance and query
    >
    > ON PROD :
    >
    > Query Plan
    >
    

    ---

    
    > SELECT STATEMENT Cost =
    > SORT GROUP BY
    > NESTED LOOPS
    > NESTED LOOPS
    > TABLE ACCESS FULL DI_PRATN_CHARGE_ITEMS
    > TABLE ACCESS BY INDEX ROWID
    > CP_INVOICE_HEADERS_ALL
    > INDEX RANGE SCAN CP_INVOICE_HEADERS_N2
    > TABLE ACCESS BY INDEX ROWID
    > CP_INVOICE_ITEMS_ALL
    > INDEX RANGE SCAN CP_INVOICE_ITEMS_N25
    >
    >
    > ON TEST :
    >
    > Query Plan
    >
    

    ---

    
    > SELECT STATEMENT Cost = 169
    > SORT GROUP BY
    > HASH JOIN
    > NESTED LOOPS
    > TABLE ACCESS BY INDEX ROWID
    > CP_INVOICE_HEADERS_ALL
    > INDEX RANGE SCAN CP_INVOICE_HEADERS_N2
    > TABLE ACCESS BY INDEX ROWID
    > CP_INVOICE_ITEMS_ALL
    > INDEX RANGE SCAN CP_INVOICE_ITEMS_PK
    > TABLE ACCESS FULL DI_PRATN_CHARGE_ITEMS
    >
    >
    >
    > and Query is
    >
    > Select
    > Nvl(ih.sub_customer_number, ih.customer_number)
    > customer_number
    > ,ih.sub_account_number
    > ,ii.inventory_item_id
    > ,ii.organization_id
    > ,Sum(ii.total_line_amount) total_line_amount
    > From apps.CP_INVOICE_ITEMS ii,
    > apps.CP_INVOICE_HEADERS ih,
    > apps.DI_PRATN_CHARGE_ITEMS ci
    > where ih.billing_period_end_date = '31-jan-2000'
    > and ii.invoice_id = ih.invoice_id
    > and ii.inventory_item_id=ci.inventory_item_id+0
    > and ii.organization_id=ci.organization_id+0
    > and nvl(ii.total_line_amount, 0) != 0
    > group by
    > Nvl(ih.sub_customer_number,
    > ih.customer_number),
    > ih.sub_account_number,
    > ii.inventory_item_id,
    > ii.organization_id
    > /
    >
    >
    >
    >
    >
    >
    > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > Brijesh Gupta
    > Oracle Production DBA
    >
    

    ---

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Author: Mohammad Rafiq
  INET: rafiq9857_at_hotmail.com

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Received on Mon Aug 13 2001 - 16:34:52 CDT