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Home -> Community -> Mailing Lists -> Oracle-L -> RE: a explain plan question
Sorry my bad, now it is crystal clear.
Bernard Polarski
From: LS Cheng [mailto:exriscer_at_gmail.com]
Sent: woensdag 31 januari 2007 10:53
To: Polarski, Bernard
Cc: ax.mount_at_gmail.com; oracle-l_at_freelists.org
Subject: Re: a explain plan question
Hi Bernard
In the execution plan it shows this:
| 4 | PARTITION RANGE ITERATOR| | | | | KEY | KEY | |* 5 | TABLE ACCESS FULL | TUH_NVPAGINA | 5992K| 211M|27159 | KEY | KEY | Since in the parse time the partition key cannot be determined we see the KEY words. I think it basically means tabla access full by partition.
On 1/31/07, Polarski, Bernard <Bernard.Polarski_at_atosorigin.com> wrote:
Still I don't understand why we have a PARTITION RAND followed by a full table scan. Why not a direct full table scan, what is the advantage of this construct
> 4 2 PARTITION RANGE (ITERATOR) > 5 4 TABLE ACCESS (FULL) OF 'TUH_NVPAGINA' (Cost=27159
"
On 1/30/07, LS Cheng < exriscer_at_gmail.com> wrote:
TUD_FEDIA is accessed first then from that it eliminates partitions
(partition start/stop KEY), the problem seems nested loop, how many rows
is TU_FEDIA returning?
"
I don't see the keyword(stop key) in the plan. I read this plan and its only speak of a partition range access that leads to a full table scan.
My only explanation is that the CBO is underlining a failed partition pruning.
Bernard Polarski
From: amonte [mailto:ax.mount_at_gmail.com]
Sent: woensdag 31 januari 2007 10:09
To: oracle-l_at_freelists.org
Subject: Re: a explain plan question
You are correct, the NL is not good, I changed to hash join and the query runs in 50 minutes.
Thanks
Alex
On 1/30/07, LS Cheng < exriscer_at_gmail.com> wrote:
doesnt look very good plan
TUD_FEDIA is accessed first then from that it eliminates partitions (partition start/stop KEY), the problem seems nested loop, how many rows is TU_FEDIA returning?
On 1/30/07, Remigiusz Soko?owski < rems_at_wp-sa.pl <mailto:rems_at_wp-sa.pl> > wrote:
>
> Execution Plan
> ----------------------------------------------------------
> 0 SELECT STATEMENT Optimizer=CHOOSE (Cost=1022392
Card=934
> Bytes=49502)
> 1 0 SORT (GROUP BY) (Cost=1022392 Card=934
Bytes=49502)
> 2 1 NESTED LOOPS (Cost=814767 Card=182275095
Bytes=9660580035)
> 3 2 TABLE ACCESS (FULL) OF 'TUD_FEDIA' (Cost=3
Card=30
> Bytes=480)
> 4 2 PARTITION RANGE (ITERATOR)
> 5 4 TABLE ACCESS (FULL) OF 'TUH_NVPAGINA'
(Cost=27159
> Card=5992606 Bytes=221726422)
>
> I was wondering how to read this plan, the order of steps.
From old
> set autotrace trace exp it seems to me that step 5 is the
first step?
>
> 5 4 TABLE ACCESS (FULL) OF 'TUH_NVPAGINA'
(Cost=27159
> Card=5992606 Bytes=221726422)
>
AFAIK the first most nested line is the first line (in this
example the
one indicated by You)
Regards Remigiusz -- --------------------------------------- Remigiusz Sokolowski <rems_at_wp-sa.pl > WP/PTI/DIP/ZAB (+04858) 52 15 770 MySQL v. 4.x Oracle v. 10.x --------------------------------------- -- http://www.freelists.org/webpage/oracle-l
-- http://www.freelists.org/webpage/oracle-lReceived on Wed Jan 31 2007 - 03:58:22 CST
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