RE: query and delete records really slow in a table

If that explain plan is for deleting one row, then it is not a good explain 
plan.  It is doing a full table scan in the child table for every row in the 
parent.  Did you analyze the tables with histograms?   (i.e. for all indexed 
columns)


Pat

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Koppelaars, Toon
Sent: Friday, October 19, 2007 8:06 AM
To: legedoos@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: query and delete records really slow in a table

Rob,

- Can you share the delete statement text?
- Is the index structure on all involved foreign keys the same (on this and the 
other database)?
- Can perform a sql-trace of both cases (fast and slow)?

Toon

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of LegeDoos
Sent: vrijdag 19 oktober 2007 14:29
To: oracle-l@xxxxxxxxxxxxx
Subject: query and delete records really slow in a table

Hi there!

We have a couple (18) of tables "linked" with foreign keys and cascading 
delete. The largest table contains < 1.000.000 records.

When deleting a record from the top level table, this is extremely slow (like 
waiting a couple of minutes). On another database (on the same server and on 
another server) deleting is fast (<1sec). Tables contain defferent data.

-There are no blocking locks
-rebuilding the indexes didn't help
-the explain plan looks ok and is the same for the different databases

0               DELETE STATEMENT optimizer=ALL_ROWS (cost=460 card=1
bytes=73)
1       0         DELETE of 'OST_STUDENT_STUDIEVOORTGANG'
2       1           HASH JOIN (SEMI) (cost=460 card=1 bytes=73)
3       2             TABLE ACCESS (FULL) of
'OST_STUDENT_STUDIEVOORTGANG' TABLE
(cost=57 card=31859 bytes=1146924)
4       2             TABLE ACCESS (FULL) of 'OST_STUDENT_EXAMEN' TABLE
(cost=199
card=55431 bytes=2050947)

-I moved all tables en indexes to another tablespace, didn't help -There are no 
errors in the alert.log.

Can anybody help?

Thanks!

Rob
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