RE: Delete Performance Issue
- From: "Ken Naim" <kennaim@xxxxxxxxx>
- To: <doodon@xxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 21 Dec 2006 14:29:21 -0500
Deleting 2.3 million rows takes time especially in 65 million rows table.
The way I might handle this is load a global temporary table with the values
returned by the subquery and "create table as select " a new table with the
data you want add the index and them swap the names. If that is not an
option try loading the values into a temp table and then doing the delete
with a not in and add an index to the runseq field.
Ken
_____
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Don Doo
Sent: Thursday, December 21, 2006 12:47 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Delete Performance Issue
Hi,
We are facing a serious performance
issue. This is a delete statement and
it takes 4 hours to delete 2.3 million
rows from a 65 million row table.
The c_trace table has only one index
(the primary key) The table is not
partitioned (we don't have the budget
to pay for partition option) Other tables
have less than 5000 rows.
The sub-query returns 3 to 6 rows
depending on the values
Query
delete from c_trace
where targetperiod= 200612
and RUNSEQ in (select
RunSeq from C_Run pr,
C_Summary ss,
C_Stage st
where pr.RunSeq = ss.RunSeq
and ss.stageType = st.stageType
and st.name = 'load'
and pr.period = 361
and ss.Active = 'yes')
The V$session_longops shows
1 select OPNAME||' '||MESSAGE||' '||ELAPSED_SECONDS from
v$session_longops
2* where sql_hash_value=2467621466
SQL> /
OPNAME||''||MESSAGE||''||ELA
----------------------------------------------------------------------------
------------
Hash Join Hash Join: : 6592 out of 6592 Blocks done 13688
Hash Join Hash Join: : 6272 out of 6272 Blocks done 12753
Hash Join Hash Join: : 6272 out of 6272 Blocks done 13594
Hash Join Hash Join: : 7488 out of 7488 Blocks done 14050
Looks like it takes 14050 seconds to complete the hash join which
matches the time taken to complete the delete.
select HASH_VALUE,CPU_TIME,elapsed_time/(1000000*60),
fetches,disk_reads,
BUFFER_GETS,ROWS_PROCESsed
from v$sql where hash_value = 2467621466
HASH_VALUE CPU_TIME FETCHES DISK_READS BUFFER_GETS ROWS_PROCESSED
---------- ---------- ------------------------- ---------- ----------
----------- --------------
2467621466 193010000 0 1265770
13820713 2325397
Oracle version 9.2.0.4
Hash_area_size 8 MB
Sort_area_size 4 MB
Statistics are current..
We are using ASSM for these tables.
I would really appreciate any ideas to improve this statement. We cannot do
a event trace
here until mid of January next year because we are behind the SLA and don't
want to make it slower.
Regards,
Don
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