I see the index skip scan is now gone from the plan.
But, there is merge cartesian inside multi level nested loops.
That is not something I would care to see in a plan for SQL that must be
quick.
Perhaps revisiting the purpose of the query and rethinking how that purpose
is to be realized is in order.
Just a thought.
On Thu, Aug 26, 2021 at 07:00 Amit Saroha <eramitsaroha@xxxxxxxxx> wrote:
Hi Andy,Jared Still
Please find the details enclosed.
Best Regards,
AMIT SAROHA
On Thu, Aug 26, 2021 at 9:42 AM Andy Sayer <andysayer@xxxxxxxxx> wrote:
Can you share the new complete plan with the connect_by_filtering hint.
The hint was more to see what Oracle thought was so expensive about this
option so we can see what we can do to help it - I imagine once we’ve done
that you won’t need the hint as well
Thanks,
Andrew
On Thu, 26 Aug 2021 at 14:40, Amit Saroha <eramitsaroha@xxxxxxxxx> wrote:
Hi Mark, Andy - There is no improvement post adding LEADING HINT but
CONNECT_BY_FILTERING the run time is improved between *.7 and .8
seconds; *which is really good but do you think any other options to
bring it down below *.5 *seconds?
Best Regards,
AMIT SAROHA
On Wed, Aug 25, 2021 at 2:33 PM Amit Saroha <eramitsaroha@xxxxxxxxx>
wrote:
Thank you, Andy, Mark for the valuable inputs. I'll try the
suggestions and revert back to you.
Best Regards,
AMIT SAROHA
On Wed, Aug 25, 2021 at 1:13 PM Andy Sayer <andysayer@xxxxxxxxx> wrote:
Hi,
Materializing any of the filters only contained in the where clauses
of the connect by queries is not a valid rewrite. Remember that where is
evaluated after the connect by and since these conditions aren't included
in the connect by conditions we can't filter them out until after all the
work is done. If the organization_id filters are valid to include in
the connect by clauses then it will likely give you a very quick win by
adding them.
It is the go_up_in_chain CTE which is taking all the time, it's much
longer than the other one as it is not using the good looking predicate
segment1
= '057825130B' to start the recursion. I would guess that it has
decided not to because it is unable to use indexes in a nice way going
this
way though the chain.
Quick sanity check, do you have an index that would cover predicates:
mtl_related_items (attr_char1, related_item_id) -- it looks like you
have an index which starts with related_item_id (MTL_RELATED_ITEMS_U1) but
I don't think this is selective enough on it's own.
If you do have that index and the plan is remaining the same, try
adding the /*+CONNECT_BY_FILTERING*/ hint to the go_up_in_chain CTE
and see where it believes the cost of doing things this way are.
Thanks,
Andrew
On Wed, 25 Aug 2021 at 14:37, Mark W. Farnham <mwf@xxxxxxxx> wrote:
So better stats might improve the plan, but if that’s a problem, I’d--
take a whack at materialized with processing of apps.mtl_related_items
mri
in both halves to present just the rows that are already pruned for
SYSDATE
BETWEEN NVL(mri.start_date, SYSDATE - 1) AND NVL(mri.end_date, SYSDATE +
1)
and
either mri.attr_char1 IN ('AN') or mri.attr_char1 IN ('A') depending
on which half.
If we’re sweating bits, a pre-pruned materialized
apps.fnd_lookup_values flv is probably tiny and you can present the rows
with the to_number on lookup_code already done to match
relationship_type_id, of course also pruning to AND flv.lookup_type =
'MTL_RELATIONSHIP_TYPES'
AND flv.meaning
LIKE 'MNAO%'
Probably apps.mtl_system_items_b msib1 and msib2 are too big to
materialize, but let Oracle decide that after you prune them both to
organization_id = 85 in a with.
From your actual counts and timing stats, you can see that line 49 is
driving your foobar number of nested loops iterations, guessing 51K and
giving 196K, while going on to discard all but 3.
So probably you want to force the join of the pruned mri and pruned
flv to take place before you join that result set to two copies of
mtl_system_items_b.
So you do THAT in a with hinted to stop oracle from undoing it,
keeping just the columns you need
from mri_flv_pruned_an
inner join mtl_system_items_b_85 msib1 ON
mri_flv_pruned_an.inventory_item_id = msib1.inventory_item_id
inner join mtl_system_items_b_85 msib2 ON
mri_flv_pruned_an.inventory_item_id = msib2.inventory_item_id
gets you down to AND CONNECT_BY_ISCYCLE = 0, which is so much easier
to read I’d do it just for clarity.
Factoring that pruning out early in the source code may significantly
improve Oracle’s plan, but it definitely removes brain pollution.
You’ll notice I intentionally didn’t look up the names of the hints
for you.
Good luck,
mwf
*From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto:
oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Amit Saroha
*Sent:* Tuesday, August 24, 2021 10:43 AM
*To:* ORACLE-L (oracle-l@xxxxxxxxxxxxx)
*Subject:* Small and complicated query run time improvement inputs
Hi All,
I have a query which takes *1.5* seconds to execute which is not
enough for my application. I must reduce the time somehow to around
*.2-.5* seconds.
Please look at the enclosed query, plan and sql monitoring report and
share the feedback to improve the time.
Best Regards,
AMIT
