RE: RE: tuning a massive delete

When tuning queries, ignore the fact that explain plan shows a cost. The optimizer finds the lowest cost it can. If you mess with hints you will almost certainly get a higher cost. I've tuned queries that ran for hours with a cost of less than 10 -- the tuned versions had costs in the hundred-billions and ran in seconds.

Secondly, you can alter session your hash_area_size up and noone will be the wiser.

Kevin

-----Original Message-----
Sent: Wednesday, September 17, 2003 12:25 PM To: Multiple recipients of list ORACLE-L

i explain planned it and it was much worse than not exists.

my understanding is hash_aj is faster when the table in the sub-query returns results that are significantly less than the one in the outer table.

ill try it, but i think exists is faster. we dont want to do an index scan here and my hash_area_size isnt real big.
>
> From: "Richard Ji" <Richard.Ji_at_ztango.com>
> Date: 2003/09/17 Wed PM 12:04:56 EDT
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Subject: RE: tuning a massive delete
>
> Try anti hash join.
>
> -----Original Message-----
> Sent: Wednesday, September 17, 2003 11:45 AM
> To: Multiple recipients of list ORACLE-L
>
>
> i have a table with 27 million records that is about 1.2 GB in size. I
have a 'staging table' with 18 million records. 16 million records have a 'delete' flag. I have indexed the column in staging with a delete flag. both tables have indexed primary keys. Is the following my fastest option or would an 'IN' be faster? Im concerned because this has been running for a while and have alot of consistent gets but no 'writes' yet which tells me its still building the join. Our sort_area_size is rather small and Im not allowed to change it which tells me we are swapping to the temp tablespace.
>
> anyway to speed this up? or is this the fastest we got?
>
>
> create table ani_prx_new parallel (degree 5) nologging
> as select *
> from ani_prx b
> where not exists (select 1 from bo_owner_stage.ani_prx a where ba_reccode
= 'V' and a.cusip = b.cusip
> and a.fund_no = b.fund_no and a.add_cymd = b.add_cymd)
>
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> Author: <rgaffuri_at_cox.net
> INET: rgaffuri_at_cox.net
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  INET: rgaffuri_at_cox.net

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