Re: Hint for self-join connect by
- From: "Alberto Dell'Era" <alberto.dellera@xxxxxxxxx>
- To: "Herring Dave - dherri" <Dave.Herring@xxxxxxxxxx>
- Date: Tue, 1 May 2007 19:35:44 +0200
That doesn't seem to tally with any of your plans - neither
has both id 5 and 6 with an asterisk. May you please
check it out and repost both plans with the predicate infos ?
It would also interesting to know num_distinct, num_null and density
(from dba_tab_columns) for the columns
acct_id, forward_surrogate_id and surrogate_id.
450k out of 70M - that's 0.6%. Maybe an index on
acct_id, forward_surrogate_id
may help the first selection, and another on
surrogate_id, forward_surrogate_id
*might* help the hierarchy visit (or at least turn the FTS
into an index FFS). Why not giving it a shot.
How many levels, on average, has your connect by ?
I meant gathering at 100% just to experiment, not as standard
practice - even if 70million is not very big, but of course it depends
on the HW and the other activities on the system.
On 5/1/07, Herring Dave - dherri <Dave.Herring@xxxxxxxxxx> wrote:
Got it:
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("from$_subquery$_001"."RN"=1)
3 - filter(ROW_NUMBER() OVER ( PARTITION BY
SUBSTR("from$_subquery$_003"."TREE",1,INSTR("from$_subquery$_003"."TREE"
,'|')-1)
ORDER BY "from$_subquery$_003"."LEV" DESC )<=1)
4 - filter(INSTR("from$_subquery$_003"."TREE",'|')>0)
5 - filter("DCH_WORK_SURR_MGMT_ONE"."ACCT_ID"='_MERGED_')
6 - filter("DCH_WORK_SURR_MGMT_ONE"."ACCT_ID"='_MERGED_')
I haven't tried gathering at 100%, mostly because there are 70 million
rows. I do plan on trying various histogram options on ACCT_ID.
As for the count of '_MERGED_' rows, its about 450,000.
Dave
___________________________________
David C. Herring, DBA | A c x i o m Delivery Center Organization
630-944-4762 office | 630-430-5988 wireless | 630-944-4989 fax
> -----Original Message-----
> From: Alberto Dell'Era [mailto:alberto.dellera@xxxxxxxxx]
> Sent: Tuesday, May 01, 2007 11:14 AM
> To: Herring Dave - dherri
> Cc: amit poddar; oracle-l
> Subject: Re: Hint for self-join connect by
>
> I think Amit was asking for the "filter predicates" section at the
> end of the explain plan ;)
>
> By the way, have you tried collecting statistics at 100%, to see
> whether that makes any difference ?
>
> How many rows (starting rows) with acct_id = '_MERGED_' there are
> in the tables - a few, many, almost all ?
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Alberto Dell'Era
"dulce bellum inexpertis"
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