Effect of RLS policy (VPD) on execution plan of a query

Hi
I have been working on tuning of few queries. A RLS policy is defined on most of the tables which appends an extra where condition (something like AREA_CODE=1). I am not able to understand the effect of this extra where clause on the execution plan of the query. In the execution plan there is no mention of the clause added by VPD. In 10046 trace it does show the policy function being executed but nothing after that.
Can someone shed some light on the issue that has VPD any effect on the execution plan of the query ? Also would it matter whether the column on which VPD is applied, was indexed or non-indexed ?
Regards,
Amardeep Sidhu

Amardeep Sidhu wrote:
I have been working on tuning of few queries. A RLS policy is defined on most of the tables which appends an extra where condition (something like AREA_CODE=1). I am not able to understand the effect of this extra where clause on the execution plan of the query. In the execution plan there is no mention of the clause added by VPD. In 10046 trace it does show the policy function being executed but nothing after that.
VPD is supposed to be invisible - which is why you get minimal information about security predicates in the standard trace file. However, if you reference a table with a security preidcate in your query, the table is effectively replaced by an inline view of the form: "select * from original_table where {security_predicate}", and the result is then optimised. So the effects of the security predicate is just the same as you writing the predicate into the query.
Apart from your use of v$sql_plan to show the change in plan and the new predicates, you can see the effects of the predicates by setting event 10730 with 10046. In current versions of Oracle this causes the substitute view being printed in the trace file.
Bear in mind that security predicates can be very complex - including subqueries - so the effect isn't just that of including the selectivity of "another simple predicate".
Can someone shed some light on the issue that has VPD any effect on the execution plan of the query ? Also would it matter whether the column on which VPD is applied, was indexed or non-indexed ?
Think of the effect of changing the SQL by hand - and how you would need to optimise the resultant query. Sometimes you do need to modify your indexing to help the security predicates, sometimes it won't make enough difference to matter.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
"Science is more than a body of knowledge; it is a way of thinking"
Carl Sagan
To post code, statspack/AWR report, execution plans or trace files, start and end the section with the tag {noformat}{noformat} (lowercase, curly brackets, no spaces) so that the text appears in fixed format.

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Sorry,
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PLAN_TABLE_OUTPUT
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Pstart| Pstop | TQ |IN-OUT| PQ Distrib |
| 0 | SELECT STATEMENT | | 16M| 3675M| | 120K (0)| | | | | |
|* 1 | FILTER | | | | | | | | | | |
|* 2 | HASH JOIN | | 16M| 3675M| | 120K (0)| | | 03,09 | P->S | QC (RAND) |
| 3 | TABLE ACCESS FULL | ORG_LOC_DM | 2261 | 13566 | | 8 (0)| | | 03,01 | S->P | HASH |
|* 4 | HASH JOIN OUTER | | 16M| 3582M| 1023M| 120K (0)| | | 03,08 | P->P | HASH |
|* 5 | HASH JOIN OUTER | | 16M| 2783M| 1041M| 102K (0)| | | 03,08 | PCWP | |
|* 6 | HASH JOIN OUTER | | 16M| 2521M| 715M| 69515 (0)| | | 03,08 | PCWP | |
| 7 | PARTITION RANGE ALL | | | | | | 1 | 14 | 03,08 | PCWP | |
| 8 | TABLE ACCESS FULL | SURT_SKU_LD_DM | 16M| 1922M| | 60988 (0)| 1 | 14 | 03,04 | P->P | HASH |
| 9 | VIEW | | 909K| 33M| | | | | 03,05 | P->P | HASH |
| 10 | SORT GROUP BY | | 909K| 19M| 62M| 1553 (0)| | | 03,05 | PCWP | |
|* 11 | HASH JOIN | | 909K| 19M| | 164 (0)| | | 03,05 | PCWP | |
|* 12 | TABLE ACCESS FULL| ORG_LOC_DM | 1131 | 6786 | | 8 (0)| | | 03,00 | S->P | HASH |
|* 13 | TABLE ACCESS FULL| INV_MOVE_SKU_LCM_DM | 909K| 13M| | 154 (0)| 60 | 60 | 03,02 | P->P | HASH |
|* 14 | TABLE ACCESS FULL | SURT_SKU_LCM_DM | 16M| 260M| | 6457 (0)| 59 | 59 | 03,06 | P->P | HASH |
| 15 | VIEW | | 1795K| 89M| | | | | 03,07 | P->P | HASH |
| 16 | SORT GROUP BY | | 1795K| 63M| 233M| 4565 (0)| | | 03,07 | PCWP | |
|* 17 | TABLE ACCESS FULL | SLS_SKU_LCM_DM | 1795K| 63M| | 599 (0)| 60 | 60 | 03,03 | P->P | HASH |
| 18 | NESTED LOOPS | | 1 | 16 | | 7 (15)| | | | | |
| 19 | TABLE ACCESS FULL | MAINT_LOAD_DT | 1 | 8 | | 1 (0)| | | | | |
|* 20 | INDEX RANGE SCAN | DAY_IDNT_I1 | 1 | 8 | | 1 (0)| | | | | |
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1 - filter("SYS_ALIAS_1"."DAY_IDNT"= (SELECT /*+ */ :B1 FROM "RDW91_DM"."MAINT_LOAD_DT" "Y","RDW91_DM"."TIME_DAY_DM" "X" WHERE
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5 - access("SYS_ALIAS_1"."LOC_KEY"="B"."LOC_KEY"(+) AND "SYS_ALIAS_1"."SKU_KEY"="B"."SKU_KEY"(+))
6 - access("SYS_ALIAS_1"."LOC_KEY"="J"."LOC_KEY"(+) AND "SYS_ALIAS_1"."SKU_KEY"="J"."SKU_KEY"(+))
11 - access("A"."LOC_KEY"="B"."LOC_KEY")
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PLAN_TABLE_OUTPUT
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost | Pstart| Pstop | TQ |IN-OUT| PQ Distrib |
| 0 | SELECT STATEMENT | | 16M| 3685M| | 94G| | | | | |
| 1 | FILTER | | | | | | | | | | |
| 2 | PX COORDINATOR | | | | | | | | | | |
| 3 | PX SEND QC (RANDOM) | :TQ10008 | 16M| 3685M| | 94G| | | Q1,08 | P->S | QC (RAND) |
| 4 | BUFFER SORT | | 16M| 3685M| | | | | Q1,08 | PCWP | |
| 5 | NESTED LOOPS OUTER | | 16M| 3685M| | 94G| | | Q1,08 | PCWP | |
| 6 | HASH JOIN | | 16M| 3424M| | 201K| | | Q1,08 | PCWP | |
| 7 | BUFFER SORT | | | | | | | | Q1,08 | PCWC | |
| 8 | PX RECEIVE | | 2261 | 13566 | | 8 | | | Q1,08 | PCWP | |
| 9 | PX SEND HASH | :TQ10001 | 2261 | 13566 | | 8 | | | | S->P | HASH |
| 10 | TABLE ACCESS FULL | ORG_LOC_DM | 2261 | 13566 | | 8 | | | | | |
| 11 | PX RECEIVE | | 16M| 3332M| | 201K| | | Q1,08 | PCWP | |
| 12 | PX SEND HASH | :TQ10007 | 16M| 3332M| | 201K| | | Q1,07 | P->P | HASH |
| 13 | HASH JOIN OUTER BUFFERED | | 16M| 3332M| 982M| 201K| | | Q1,07 | PCWP | |
| 14 | HASH JOIN OUTER | | 16M| 2733M| 735M| 127K| | | Q1,07 | PCWP | |
| 15 | PX RECEIVE | | 16M| 1934M| | 75785 | | | Q1,07 | PCWP | |
| 16 | PX SEND HASH | :TQ10004 | 16M| 1934M| | 75785 | | | Q1,04 | P->P | HASH |
| 17 | PX BLOCK ITERATOR | | 16M| 1934M| | 75785 | 1 | 14 | Q1,04 | PCWC | |
| 18 | TABLE ACCESS FULL | SURT_SKU_LD_DM | 16M| 1934M| | 75785 | 1 | 14 | Q1,04 | PCWP | |
| 19 | PX RECEIVE | | 1450K| 71M| | 3892 | | | Q1,07 | PCWP | |
| 20 | PX SEND HASH | :TQ10005 | 1450K| 71M| | 3892 | | | Q1,05 | P->P | HASH |
| 21 | VIEW | | 1450K| 71M| | 3892 | | | Q1,05 | PCWP | |
| 22 | SORT GROUP BY | | 1450K| 53M| 188M| 3892 | | | Q1,05 | PCWP | |
| 23 | PX RECEIVE | | 1450K| 53M| | 562 | | | Q1,05 | PCWP | |
| 24 | PX SEND HASH | :TQ10002 | 1450K| 53M| | 562 | | | Q1,02 | P->P | HASH |
| 25 | PX BLOCK ITERATOR | | 1450K| 53M| | 562 | 60 | 60 | Q1,02 | PCWC | |
| 26 | MAT_VIEW ACCESS FULL| SLS_SKU_LCM_DM | 1450K| 53M| | 562 | 60 | 60 | Q1,02 | PCWP | |
| 27 | PX RECEIVE | | 652K| 24M| | 1150 | | | Q1,07 | PCWP | |
| 28 | PX SEND HASH | :TQ10006 | 652K| 24M| | 1150 | | | Q1,06 | P->P | HASH |
| 29 | VIEW | | 652K| 24M| | 1150 | | | Q1,06 | PCWP | |
| 30 | SORT GROUP BY | | 652K| 14M| | 1150 | | | Q1,06 | PCWP | |
| 31 | HASH JOIN | | 652K| 14M| | 128 | | | Q1,06 | PCWP | |
| 32 | BUFFER SORT | | | | | | | | Q1,06 | PCWC | |
| 33 | PX RECEIVE | | 1131 | 6786 | | 8 | | | Q1,06 | PCWP | |
| 34 | PX SEND HASH | :TQ10000 | 1131 | 6786 | | 8 | | | | S->P | HASH |
| 35 | TABLE ACCESS FULL | ORG_LOC_DM | 1131 | 6786 | | 8 | | | | | |
| 36 | PX RECEIVE | | 652K| 10M| | 118 | | | Q1,06 | PCWP | |
| 37 | PX SEND HASH | :TQ10003 | 652K| 10M| | 118 | | | Q1,03 | P->P | HASH |
| 38 | PX BLOCK ITERATOR | | 652K| 10M| | 118 | 60 | 60 | Q1,03 | PCWC | |
| 39 | MAT_VIEW ACCESS FULL| INV_MOVE_SKU_LCM_DM | 652K| 10M| | 118 | 60 | 60 | Q1,03 | PCWP | |
| 40 | PARTITION RANGE SINGLE | | 1 | 17 | | 8609 | 59 | 59 | Q1,08 | PCWP | |
| 41 | TABLE ACCESS FULL | SURT_SKU_LCM_DM | 1 | 17 | | 8609 | 59 | 59 | Q1,08 | PCWP | |
| 42 | NESTED LOOPS | | 1 | 16 | | 6 | | | | | |
| 43 | TABLE ACCESS FULL | MAINT_LOAD_DT | 1 | 8 | | 1 | | | | | |
| 44 | INDEX RANGE SCAN | DAY_IDNT_I1 | 1 | 8 | | 5 | | | | | |
Note
- 'PLAN_TABLE' is old version
- cpu costing is off (consider enabling it)

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Thanks.

H.Mahmoud wrote:
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System version : HP-UX v1Hard to say. You're using a very old and deprecated version of the database, and one that was known to contain bugs.
9.2.0.7 was really the lowest version of 9i that was considered to be 'stable', but even so, it's old and lacking in many ways.
Consider upgrading to the latest database version at your earliest opportunity. (or at least apply patches up to the latest 9i version before querying if there is bugs in your really low buggy version)

Explain SQL Query execution plan: Oracle

Dear Masters,
Kindly help me to understand execution plan for an SQL statement. I have following SQL execution plan for a query in system. How should I interpret it. I thank You in advace for your guidance.
SELECT STATEMENT ( Estimated Costs = 1.372.413 , Estimated #Rows = 0 )
       5 NESTED LOOPS
         ( Estim. Costs = 1.372.413 , Estim. #Rows = 3.125 )
         Estim. CPU-Costs = 55.798.978.498 Estim. IO-Costs = 1.366.482
           2 TABLE ACCESS BY INDEX ROWID MSEG
             ( Estim. Costs = 1.326.343 , Estim. #Rows = 76.717 )
             Estim. CPU-Costs = 55.429.596.575 Estim. IO-Costs = 1.320.451
             Filter Predicates
               1 INDEX RANGE SCAN MSEG~R
                 ( Estim. Costs = 89.322 , Estim. #Rows = 60.069.500 )
                 Search Columns: 1
                 Estim. CPU-Costs = 2.946.739.229 Estim. IO-Costs = 89.009
                 Access Predicates
           4 TABLE ACCESS BY INDEX ROWID MKPF
             ( Estim. Costs = 1 , Estim. #Rows = 1 )
             Estim. CPU-Costs = 4.815 Estim. IO-Costs = 1
             Filter Predicates
               3 INDEX UNIQUE SCAN MKPF~0
                 Search Columns: 3
                 Estim. CPU-Costs = 3.229 Estim. IO-Costs = 0
                 Access Predicates

Hi Panjak,
Yeahh, there's a huge unperformatic SQL statment, what I can see from this acces plan is:
1 DBO decided to start the query on index R on MSEG, using only part of the index (only one column) with no good uniqueness, accessing disk IO-Costs for this (60mi records), and expecting many interactions (loops) in memory to filter, see CPU-Costs.
So with the parameters you gave to SQL, they start in a very bad way.
2 After that program will access the MSEG commanded by what was found on First step, also with a huge loading from DB and filtering (another where criteria on MSEG fields, not found on index R), reducing the result set to 76.717 rows.
3/4 With this, program goes direct to primary key index on MKPF with direct access (optimized access) and follow to access database table MKPF.
5 At last will "loop" the result sets from MSEG and MKPF, mixing the tuplas generating the final result set.
Do you want to share your SQL, the parameters you are sending and code which generate it with us?
Regards, Fernando Da Ró

About Execution Plan in OBIEE

Friends,
As we know when creating the BMM layer we can, for ex., create one logical table
which includes columns from two or more different physical tables and OBIEE generates
smth like a view internally.
But what about the execution plan of the query?
What happens if the size of the table chnages and the old plan is not that good anymore?
Is it somehow possible to control the Execution Plan, maybe in BMM layer, in OBIEE?
Thanks in advance.

"The performance problem is not in the writting of the query but on its path (execution plan). In the way where the database will retrieve the data."
I wouldnt say that its always the way WHERE the database will retrieve data but HOW as well, sometimes.
Indeed a lot of options availbale to speed up the preformance of a query but during my own year old
experience with Oracle Ive come across not few scripts that didnt require creation of any temporary table,
materilaized views or smth. All I needed to do is just rewrite the query and thats it.
"....execute the best explain plan...." Personally I came across a lot of queries with the tables having the freshest statistics and so on that Oracle would choose not the best plan and the one it chose didnt execute that fast as if I would set up my own plan for it.
Yes the internal algorithm may decide that this plan is the best but as experience show its not always true.
All I was asking is if there is a way to control the plan in OBIEE or not........

Effect of RLS policy (VPD) on execution plan of a query

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