I have a weird optimizer behaviour on a 10.2.0.4 db.When i add "+0" or "-0" to a number predicate, the optimizer produces 2 differents plans. I dont see why. Here are the statements:
A -First statement with suboptimal plan :
SELECT /*KO*/ TFXPPRODUCT.PRODUCTID,
TFXPPRODUCT.PRODUCTTYPE,
VFUTFIX.Datech,
TFXPPRODUCT.SHORTLABEL,
VFUTFIX.TAUCPN,
VFUTFIX.Tik,
[code]....
The following sequence of simple statements shows me how Analytics and Predicate Pushing appear to work. But when I go from constant tests to a join with the same data as a row instead of a constant value, the Predicate Pushing stops.
I have a table with 9 million rows in it. It takes about 90 seconds to scan.
13:25:11 SQL>
13:25:11 SQL> select count(*) thecount from lv_pln_usge_fact ;
THECOUNT
----------
8681388
1 row selected.
Elapsed: 00:00:32.28
If I run an analytic that counts all rows in the table I can see that easy enough. This exampe as I understand it, scans the table (I know this because if for no other reason, it take 90 seconds to get an answer), then after scanning all rows, counts them and adds the count to each row. There are in fact 9500 or so rows with the values of lv_rqst shown. Instead of seeing all 9500 rows, I distinct it to get only one. See how the count shows all rows in the table.
From this we see that the predicate is not pushed into the inner query to filter rows. If it had, the analytic would have produced a number like 9500 not 9 million. I have no issue with this as this is how Analytics are documented work.
13:25:43 SQL> select distinct *
13:25:43 2 from (
13:25:43 3 select LV_RQST
13:25:43 4 ,count(*) over () thecount
[code]..
We can see how filter does happen with an analytic. We push the predicate into the inner query and all of a sudden we get a count of only those rows for the specific request. Thus we see the basics of how analytics work, particularly with respect to predicate pushing. There is not real rocket science here. The filter removed rows before the analytic counted them. This too is how Analytics are documented to work.
13:27:02 SQL> select distinct *
13:27:02 2 from (
13:27:02 3 select lv_rqst,count(*) over () thecount
13:27:02 4 from lv_pln_usge_fact
13:27:02 5 where lv_rqst = '746780192'
[code]...
So far we have been doing "all rows" analytics. Now we use a PARTITION clause to group the data. Notice the rowcount. It is the count for just the lv_rqst. Do not be fooled. This is because the PARTITION column says to synchronize the analytic count to the data for its associated row. Thus the counts will be grouped by LV_RQST. Whether we had the predicate on the outside of the query or not, for this specific lv_rqst shown we would still get this count. This is not proof that we did any filtering with the predicate lv_rqst = '746780192'.
However, notice the speed of the query. It gets done so fast, that there is no way it is scanning the table. I know there is an index that starts with LV_RQST so I conclude that the index was used which I believe means the predicate was in fact PUSHED into the inner query. Thus I think we did in fact filter the rows to just this single LV_RQST value and we also accessed the table using the predicate as well which became an index range scan instead of full table scan. My biggest point is we were able to use the index to get the data we want, not scan the table and this was made so because we added the LV_RQST column to the OVER clause as part of the PARTITION BY expression.
13:27:03 SQL> select distinct *
13:27:03 2 from (
13:27:03 3 select LV_RQST
13:27:03 4 ,count(*) over (partition by lv_rqst) thecount
[code]...
Now I add an additional column to the inner query, and an additional predicate against that column to the outer query. We know that 9539 is the count of all rows where LV_RQST='746780192' as we have seen that before above. I also know the data and know about half say Y and half say N for this indicator column. This query gives the right answer. I just put it here are additional demonstration of the way analytics work. It demonstrates that the new predicate is not pushed into the innser query to filter rows. Again this is how Analytics are documented to work.
It used the index to range scan only the rows where LV_RQST='746780192'. So only those predicates that have their columns in the anlytics OVER clause are allowed to be pushed into the query for filtering and accessing purposes.
13:27:03 SQL> col LV_PLN_USGE_DEL_IND format a20 trunc
13:27:03 SQL> select distinct *
13:27:03 2 from (
13:27:03 3 select LV_RQST
[code]...
This next query shows a little more clarity. If we add the indicator column to our OVER clause then the rowcount changes to be the number of rows where LV_RQST='746780192' AND lv_pln_usge_del_ind = 'N'. So by putting the column into the OVER expression, Oracle decides to push the predicate down into the inner query and filter the data before the analytic count is done. Again this just demonstrates for clarity how it works. I think I am describing it right anyway.
And once again the speed clearly indicates that an index range scan was done using LV_RQST='746780192'. Recall I said there is an index that starts with this column.
13:27:03 SQL> select distinct *
13:27:03 2 from (
13:27:03 3 select LV_RQST
13:27:03 4 ,LV_PLN_USGE_DEL_IND
[code]...
NOW WE COME TO MY PROBLEM.Instead of using the constant value '746780192' we are going to create a one column one row table that has this value in it. We are then going to join to the the analytic subquery instead of doing a contant test against it.
13:27:03 SQL> create table kevt1
13:27:03 2 (
13:27:03 3 lv_rqst varchar2(10) not null
13:27:03 4 )
13:27:03 5 /
Table created.
Elapsed: 00:00:00.06
13:27:03 SQL>
13:27:03 SQL> insert into kevt1 values ('746780192')
13:27:03 2 /
1 row created.
Elapsed: 00:00:00.00
13:27:03 SQL>
13:27:03 SQL> commit
13:27:03 2 /
Commit complete.
Elapsed: 00:00:00.00
This query is in my mind the same query we did before but we loose the use of the index and go back to doing a FULL TABLE SCAN.
13:27:03 SQL> select distinct x.*
13:27:03 2 from (
13:27:03 3 select LV_RQST
[code]...
For a little bit more clarity, two more queries. Pay attention to how long it takes, and to how the additional joins affect things. Notice, particularly with the last statement, that the join criteria is being pushed into the inner query with the analytics. Otherwise how did it get that count?
14:55:21 SQL> select distinct x.*
14:56:16 2 from (
14:56:16 3 select LV_RQST
14:56:16 4 ,LV_PLN_USGE_DEL_IND
[code]...
So after looking at all this, here is my question: How do I get Oracle the use the index and nested loop join to the table lv_pln_usge_fact. We know Oracle pushes the predicates down when the columns are referenced in the OVER expression because we see that in several places. We also know the CBO can do a nested loop join with index access on LV_RQST because it does it when we use a constant test. But it won't use the index and nested loop when we do a join to a table with the same data, no matter how much rewriting or hinting I do.
I tested this in 9i/10g/11g and got same behavior in all three places.
I am executing the query below:
INSERT INTO temp_vendor(vendor_record_seq_no,checksum,rownumber,transaction_type,iu_flag)
SELECT /*+ USE_NL ( vd1 ,vd2 ,vd3 ) leading ( vd1 ,vd2 ,vd3 , tvd) */ vd1.vendor_record_seq_no, tvr.checksum, tvr.rownumber, tvr.transaction_type, 'U'
FROM vendor_data vd1,
vendor_data vd2,
vendor_data vd3,
(SELECT rownumber,
[code]....
It is taking different approaches (execution plans) while executing for same set of parameters. Due to which sometimes it executes successfully, but sometimes it fills all TEMP space and get failed. I am pasting both the execution plan (different from expalin plan) below:
I. Successfull Execution Plan:
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | | | 65612 (100)| | | |
|* 1 | HASH JOIN | | 1 | 6121 | 65612 (1)| 00:13:08 | | |
[code]....
II. Failed with TEMP space Execution Plan:
--------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
--------------------------------------------------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | | | 1967 (100)| | | |
|* 1 | FILTER | | | | | | | |
| 2 | SORT GROUP BY | | 1 | 8233 | 1967 (3)| 00:00:24 | | |
|* 3 | HASH JOIN | | 1 | 8233 | 1966 (3)| 00:00:24 | | |
[code]....
We have a query which makes Oracle behave very strangely. It is a straight-forward join between four tables of about 30.000 rows each, with some simple comparisons and some NOT LIKE:s.
When we run this query, it either takes about 1 second or more than 1.000 seconds to run and return the approximately 5.000 rows of the result. If we run the same query over and over again, it fluctuates back and forth between two different execution plans, apparently at random, 3 times out of 4 selecting the 1.000 second version and 1 time out of 4 the 1 second version.
There are no other connections to the database, the schema is not modified, the data is identical, the query is identical, and the response is identical, but the execution time alternates between 1 second and 1.000 seconds.On the same database instance we have another schema which is identical, but with slightly less data, which is used for development. The 1.000 second run times did not happen in that schema, but only in the test system's database.
Therefore we would REALLY like to understand what happens and why, so that we can avoid triggering this in the future. We could try locking the 1 second execution plan, but then we're afraid of doing the same thing wrong again in the future.
Here are the two execution plans that Oracle switches between, more or less at random:
Rows (1st) Rows (avg) Rows (max) Row Source Operation
---------- ---------- ---------- ---------------------------------------------------
5455 5455 5455 HASH JOIN (cr=15663 pr=10536 pw=0 time=855673 us cost=82273 size=2707430769293 card=14028138701)
79272 79272 79272 TABLE ACCESS FULL GROUPS (cr=1008 pr=0 pw=0 time=22154 us cost=277 size=10693 card=289)
[code]...
Rows (1st) Rows (avg) Rows (max) Row Source Operation
---------- ---------- ---------- ---------------------------------------------------
5455 5455 5455 HASH JOIN (cr=15664 pr=0 pw=0 time=778178696 us cost=30838477 size=741611997206725 card=3842549208325)
375411 375411 375411 TABLE ACCESS FULL GROUP_GROUPS_FLAT (cr=3782 pr=0 pw=0 time=51533 us cost=1029 size=25152738 card=375414)
[code]...
The query:
select g.ucid, a.ucid
from account a, groups g, group_members gm, group_groups_flat ggf
where a.ucid = gm.ucid_member
and gm.ucid_group = ggf.ucid_member
[code]...
And excerpts from the schema:
CREATE TABLE "PDB"."GROUPS"
(
"UCID" VARCHAR2(256 BYTE),
"UNIX_GID" NUMBER(*,0),
[...]
[code]...
When we use the AUTOTRACE / EXPLAIN PLAN we can see the (estimated) best execution plan the Optimizer found for our SQL Command. Is there a way to display all alternate execution plans the Optimizer has considered ?
View 1 Replies View RelatedI am adding condition in color to my existing query but my query taking too long time after that. This condition calculates last 3 month end dates from given COB (20110516).
SUMMARY is my summarized table and COB is my reference table
Without adding condition in query it gives
INDEX (RANGE SCAN)--PK_SUMMARY(INDEX(UNIQUE))
After adding condition in query it gives
INDEX(FAST FULL SCAN)--PK_SUMMARY(INDEX(UNIQUE))
how can i keep RANGE SCAN even after adding my new conditions?
SELECT
distinct
COB.COB_ID_C,
SUMMARY.SUMM_COB_ID_C
FROM
[code]...
I have the below query which is doing FTS and is very expensive causing load to timeout.
I did my analysis and found that table is having large number of records and hence FTS is taking long time causing timeout from app side.
I proposed to have this table partitioned but this is still pending with business and they in meantime want some solution other solution to fix this issue.
below is the query and plan
SELECT TRANSACTION_LOG.ID, TRANSACTION_LOG.USER_IDENTIFIER, TRANSACTION_LOG.START_TIME, TRANSACTION_LOG.END_TIME, TRANSACTION_LOG.REQUEST, TRANSACTION_LOG.RESPONSE ....
how many number of times the sql's had been executed/run in an oracle session. Executions in V$sql, is it the right place to look at? Will it give the number of times the sql has been executed in a particular session?
View 3 Replies View RelatedWhen viewing SQL statements in Top Activity in OEM, I am only able to see the Explain Plan for the most recent statement. Is there a setting to increase the number execution plans kept?
View 1 Replies View RelatedIs there any way i can Get how many rows are processing with UPDATE statement while the Update statement is still running.
View 2 Replies View RelatedCan we add 10000 days in SYSDATE using + operator ?
Quote: This I can test it but I don't have database access now that's why I am asking this question
Looking to understand the difference between instance tuning and database tuning.
What is the difference between these two tuning exercises? I understand that an instance is memory based structures (logical) where as database consists of physical structures.
However, how does one tune a database the physical structure? Does it have to do with file placements/block sizes etc. Would you agree that a lot of that is taken care by ASM now in 11g? What tools are required/available (third party as well as oracle supplied) for these types of tuning scenarios?
The below sql is giving different number of result sets while adding further columns in select clause.i.e After adding the columns 4,5,6 in the below query its giving different number of result set.In this case the result set count would be 5.
Before adding the columns 4,5,6,the result set count was 11.
SELECT PAYMENT_METHOD_MAP.NETTINGGROUP_ID,
PAYMENT_METHOD_MAP.CREDITPAYMENTMETHOD_CD,
PAYMENT_METHOD_MAP.DEBITPAYMENTMETHOD_CD,
PAYMENT_METHOD_MAP.AGENT_ID,
SETTLEMENT.NETTINGGROUP_ID,
SETTLEMENT.SETTLEMENTDATE
[code]....
I have a stored procedure that stores a record containing a date field.
The syntax is
insert into audit_log values (lv_sequence, sysdate, REC_TYPE, p_pln_id, OPER_UPDATE, log_message);
This works except that the date stored in the record has a time of 00:00. This does not work well for an audit log.
How can I store a date that includes a time?
An interesting fact is...I used this same command in SQL Developer to store a record and the date stored did have a time???
select 1 from dual
where 1 >= any (select 1 as col from dual
union all
select 1 from dual
union all
select 1 from dual);
Output:
------
1
-
1
[code]....
Why the sub query factoring produces different result.Is sub query factoring can be a problem and leads to different result?
I have two tables with 113M records in DWH_BILL_DET & 103M in prd_rerate_chg_que and Im running following merge query, which is running for 13 hrs to update records, which is quiet longer time.
SQL> explain plan for MERGE /*+ parallel (rq, 16) */
INTO DWH_BILL_DET rq
USING (SELECT rated_que_rowid,
detail_rerate_flag_code,
rerate_sel_key,
[code].....
How the length of column width effects index performance?
For example if i had IOT table emp_iot with columns:
(id number,
job varchar2(20),
time date,
plan number)
Table key consist of(id, job, time)
Column JOB has fixed list of distinct values ('ANALYST', 'NIGHT_WORKED', etc...).
What performance increase i could expect if in column "job" i would store not names but concrete numbers identifying job names.
For e.g. i would store "1" instead 'ANALYST' and "2" instead 'NIGHT_WORKED'.
I have a question about database fragmentation.I know that fragmentation can reduce performance in query times. The blocks are distributed in many extents and scans process takes a long time. Oracle engine have to locate the address of the next extent..
I want to know if there is any system view in which you can check if your table or index has high fragmentation. If it's needed I will have to re-create, move or rebulid the table or index, but before I want to know if the degree of fragmentation is high.
Any useful script or query to do this, any interesting oracle system view?
There is a simple way to increase the performance of a query by reducing the row-size of the table it hits. I used it in the past by dividing the table into smaller parts and querying respective smaller table in each query.
what is this method called ? just forgot the method and can't recall it. what this type of row-reduction optimization is called ?
How many records could I have in a single table without performance degradation with Standard Edition without partitioning with cutting-edge server (8 or 12 cores, 72 GB RAM, FC 4 Gbit, etc...) and good storage?
300 Millions in only one table with 500K transactions / day is too much?
Simple database with simple schema.
How many records begin to be too many?
Testing our 9i to 11g upgrade, we've imported the entire DB into the new machine.We've found that certain procedures are really suffering performance problems. BUT, we've also found, that if we check out a production copy of the procedure from our source code control, and reinstall it, the performance issue goes away. Just alter the procedure and recompiling does NOT work.
The new machine where the 11g database exists is slightly different than the source, but it's not like we have this problem with every procedure. It's only a couple.
any possible reason that we'd have to re-install a procedure to correct a performance problem?
I need to check the package performance and need to improve the package performance.
1. how to check the package performance(each and every statement in the package)?
2. In the package using the delete statement to delete all records and observed that delete is taking long time to delete all the records in the table(Table records 7000000). This table is like staging table.Daily need to clean the data before inserting the data into it. what can I use instead of Delete.
Somewhere I read that we should not use hints in Oracle production environments, but we can use hints in the development environment and on achieving the desired execution plan we can adjust the 'statistics' to follow that plan without hints.
Q1. If it is true what statistics do we adjust for influencing the execution plan and how?
For example, I have the following simple query:
select e.empid, e.ename, d.dname
from emp e, dept d
where e.deptno=d.deptno;
emp.empid, emp.deptno and dep.deptno columns have indexes and the tables have the standard structure as found in the basic oracle examples.
If I look at the execution plan of the above query then I see that the driving table is empand the driven table is dept.Also the type of join that is taking place is 'Nested Loop'.
Questions: With respect to the above query,
Q 2. If I want to make dept the driving table and emp the driven table then how can I adjust the statistics to achieve that?
Q 3. If I want to use hash join instead of a nested loop join then then how can I adjust the statistics to achieve that?
I can put the ordered and the use_hash hint to effect this but again I have heard that altering statistics is a more robust way to control an execution plan as compared to hints.
I have an issue with export(expdp).
When i exporting an user using expdp utility, the load the on the server is going up-to 5. The size of the database is 180GB. Below is the command that i use for export.
expdp sys/xxxx directory=dbpdump dumpfile=expdp_trk_backup.dmp logfile=expdp_trk_backup.log exclude=statistics schemas=trk
Do i need any look into any memory parameters for this?
The following query gets input parameter from the Front End application, which User queries to get Reports.There are many drop down boxes like LOB, FAMILY, BRAND etc., The user may or may not select values from drop down boxes.
If the user select any one or more values ( against each drop down box) it has to fetch all matching values from DB. If the user does'nt select any values it has to fetch all the records, in this case application will send a value 'DEFAULT' (which is not a value in DB ) so that the DB will fetch all the records.
For getting this I wrote a query like below using DECODE, which colleague suggested that will hamper performance.From the below query all the variables V_ are defined in procedure which gets the values selected by user as a comma separated string here V_SELLOB and LOB_DESC is column in DB.
DECODE (V_SELLOB, 'DEFAULT', V_SELLOB, LOB_DESC) IN
OPEN v_refcursor FOR
SELECT /*+ FULL(a) PARALLEL(a, 5) */
*
FROM items a
WHERE a.sku_status = 'A'
[code]...
what the principal things to look at when we have for the same query different performance results are?I have 2 different bases: the plan and data are the same but performance results are very differents.
View 10 Replies View RelatedI am sure I read somewhere that it is possible in 11g2 to store Predicate Fragments that work in a similar way to Functions for use in SQL queries?
I think the idea is that instead of defining a function that will form part of a predicate restriction you can define the SQL and then just reference it in your existing code.
For example, lets say I have 10 queries of varying types that only act the subset of ACTIVE customers. An 'ACTIVE' customer is one who has an order in the last 6 months OR receives a catalogue. In terms of SQL this is represented by a couple of table joins and and few 'AND' clauses.
In order to determine the active customers I can use a function in the predicate section of my 10 queries, but I don't want to do this for various reasons (context switching,tuning, etc).
Neither do I want to have to change the PROCEDURE declarations for the procs that store my 10 queries in order to pass in the portion of the SQL that would restrict the data set to ACTIVE customers.
I could just add the required SQL to each of the queries but this means if the definition of ACTIVE alters I have 10 changes to make. Is there a way that that predicate lines that select for 'ACTIVE' can somehow be declared and then this declaration referenced in my SQL queries?
are the most important performance keys we have to calculate or take in account to preserve or to increase the DB performance in terms of response times, and whatsoever according to performance ?
View 8 Replies View Relatedload data in multiple table using sql loader. I have IN predicate which i don't know is allowed in the sql loader or not
my control file and is as below
LOAD DATA
INFILE 'c: empdemo05.dat'
BADFILE 'c: empad05.bad'
DISCARDFILE 'c: empdisc05.dsc'
REPLACE
[code]....
i am getting below error when executing above error
SQL*Loader-350: Syntax error at line 5.
Expecting "(", found keyword when.
WHEN DEPTNO IN ('
We're using Oracle 10g for development purposes. I have 2 same schema with approximately same data. I'm running same query on 2 schemas and I see that the first schema runs the query around 20sec and the 2.schema less than 1 sec. I thought first that there may be missing constraints or indexes but all are the same.
I checked the plan for the 2 schemas and I see that the plan is different.
Here is the query:
SELECT ccc.ComponentId AS "ComponentId", ccp.Code AS "ParentCode", ccc.Code AS "ChildCode" FROM CatalogueComponent ccp INNER JOIN CatalogueComponent ccc ON ccp.ComponentId = ccc.ParentComponentId WHERE ccc.ComponentId IN (20934777, 1594747)
I'm sending also the 2 output of PLAN results from 2 different schemas.
what should I do to fix the problem with the NAFBCA schema.
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