Performance Tuning :: Force Index Unique Scan?
Jun 14, 2012Is there any hint to force "Index Unique Scan" over "Index Range Scan".
My query is generating different plans with the above two, and very slow when it uses "Index Range Scan".
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Performance Tuning :: How To Force SQL To Use Index Range Scan
Jul 15, 2011How can i force a sql use index range scan?
View 10 Replies View RelatedPerformance Tuning :: Force Index If Table Not Using Index?
Aug 9, 2013How to force an index if the table not using the index?
View 10 Replies View RelatedPerformance Tuning :: Force Subquery To Use Index?
Aug 5, 2010I have the following query:
Select
tag0.TAG_VALUE pid, tag1.TAG_VALUE, tag2.TAG_VALUE From TAGGER.TAGGABLE_RESOURCE r
, TAGGER.TAG tag0
, TAGGER.TAG tag1
, TAGGER.TAG tag2
where 1=1
[code]....
This runs in about 400ms. Now I replace this:
ANDtag0.TAG_TYPE in (4602, 5228)
ANDtag1.TAG_TYPE in (4612, 5225)
ANDtag2.TAG_TYPE in (4613, 5226)
with this:
ANDtag0.TAG_TYPE in (select COLUMN_VALUE from ( select * from table( TAGGER.GET_IDS_OF_SIMILAR_TAG_TYPES('Patient ID') ) x1 ))
ANDtag1.TAG_TYPE in (select COLUMN_VALUE from ( select * from table( TAGGER.GET_IDS_OF_SIMILAR_TAG_TYPES('Patients Sex') )x2 ))
ANDtag2.TAG_TYPE in (select COLUMN_VALUE from ( select * from table( TAGGER.GET_IDS_OF_SIMILAR_TAG_TYPES('Patients Birth Date') ) x3 ))
So instead of hard coding the IDs there is a function that looks them up. The function itself is reporting that it runs in 0ms. But when I run the new query:
Select
tag0.TAG_VALUE pid, tag1.TAG_VALUE, tag2.TAG_VALUE From TAGGER.TAGGABLE_RESOURCE r
, TAGGER.TAG tag0
, TAGGER.TAG tag1
, TAGGER.TAG tag2
where 1=1
[code]....
it takes around 6s to run. I have looked at the explain plans it it seems as though the function based approach is triggering a full table scan of 'TAG'.
I have tried it with query hints to use index, but it doesn't change the execution plan, or the query time.
The explain plan for the quick query is:
PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------
Plan hash value: 1031492929
---------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
[code]....
And the slow one is:
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Plan hash value: 2741657371
----------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |Te
----------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 20M| 1602M|
[code]....
Performance Tuning :: How To Verify If A Row Exists (index Range Scan)
Oct 18, 2011In the link below [URL] Thomas kyte has said, use the CBO and select /*+ FIRST_ROWS */ primary_key from table where rownum = 1; it'll read the index and stop at the first row. very fast on a big empty table (as the index is small and empty).
very fast on a big full table as the index is just read to find the first leaf node and then "stop".
It gives faster result if the primary key is used. But what if we have a table with around 1000 million rows and for the predicates there is a index range scan on the table.
What if we have a table say big_table (10000000000 rows) and the sql is something like
select /*+ first_rows */ 1 /* id, attribute_id*/
from big_table
where attribute_name ='Gross Premium'
and value ='10000'
and version_date is null
and rownum=1; --it's taking around 3 min
We observed that in such case there will be a range index scan for the index on the predicates. For a particular id there may be different values for attribute 'Gross Premium' and may have multiple versions.
How I would tune such a query where the purpose is to check if at least 1 records exists in the table for the input?
Performance Tuning :: Composite Index - Explain Plan Full Table Scan On Lookup_fein?
May 12, 2011I have created an non unique index lk_fein on lookup_fein( code,map_id,trash). When I check the explain plan it does a full table scan on lookup_fein. if I force it to use index by it does and the cost also decreases.
SQL> SELECT WORK_FEIN,
2 NON_FEIN ,
3 FI_FEIN ,
4 MFEIN ,
5 TOTAL_FEIN ,
[code]...
Performance Tuning :: Force Optimizer To Consider All Join Permutations?
Oct 14, 2013I'm looking to see if there is a way (fully expecting it to be an underscore, or two...) to force the optimizer to keep churning until all permutations are exhausted.I'm aware that it, to paraphrase, cuts out when it's spent more time parsing than it would just running it based on it's estimates.
I've got some irritating problems with xml rewrite, xml indexes and access paths/cardinalities etc and I'm really needing the entire thing considered as a one off for debugging this. I've already cranked up the maximum permutations to the max but it's not enough, it shorts out after 5041 permutations (I'd set that to 80000 max).
I know you'd not want to do this in the real world but I cant get the damned thing to run the plan I want in a 10053 so I can see the values it has there. I know I can hint it, but I'm trying to ascertain why it's not even considering it in a "normal" parse.
Performance Tuning :: Row ID Range Scan
Dec 19, 2011I want to make full table scan of my query so that I can execute it using parallel option & the query will get completed in few mins. Even though I used this hint "/*+ parallel(t2,4) full(t2) */, the query is executing with 8 parallel processes but it is going for "Rowid Range Scan" and it is taking more time to complete. How to make this query to go for full table scan instead of "Rowid Range Scan" so that this query can be tuned.
SELECT /*+ parallel(t2,4) full(t2)*/ID, COUNT (1) FROM acnt_transact t2 GROUP BY ID;
Performance Tuning :: How To Keep RANGE SCAN Even After Adding New Conditions
Aug 29, 2011I 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]...
Performance Tuning :: Full Table Scan - Query Without Where Clause?
Jul 11, 2013Below query is degrading the performance of database. As we know that, without where clause, query do full table scan.Now, it is written to generate the sequence no.
SQL> explain plan for
2 SELECT NVL(MAX(P.NUM_SERIAL_NO), 0) + 1 FROM CNFGTR_IRDA_ENVELOPE_DTLS P
3 /
Explained.
SQL> select * from table(dbms_xplan.display());
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Plan hash value: 3345343365
------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------------
[code].....
Index is not created on the column.
Performance Tuning :: Select Partition - Oracle To Scan Blocks
Sep 15, 2011I was confused by partitioed table, when i select a partition of table, how does oracle to scan blocks? it scan all blocks of table or scan a single partition blocks only?
SQL> Explain Plan For
2 Select Count(1) From Tb_Hxl_List Partition(p_L3);
Explained.
SQL> Select * From Table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 18 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | | |
| 2 | PARTITION LIST SINGLE| | 33115 | 18 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL | TB_HXL_LIST | 33115 | 18 (0)| 00:00:01 |
Performance Tuning :: Local Index Versus Global Index On Partitioned Table
Jun 28, 2011I have a huge table (about 60 gb) partition over range. The index on this table is global index created on 4 columns together. I have a query which is running very slowly. The explain plan is showing the use of this global index.Explain plan is not showing pstart and pend because the index is global.
View 6 Replies View RelatedPerformance Tuning :: Index With NVL / Query Is No Longer Using Index
Nov 19, 2010I have a query which had a join:
a.c1=b.c1 and a.c2=@var
where @var is user supplied input at runtime...We had a index on a.c2 . The CBO would use this index to generate an opitimised query plan.We found some records from table "b" were dropping due to inner join. So we made a change in join. It'd be like
a.c1(+)=b.c1 and nvl(a.c2,@var)=@var
This query is no longer using the index, instead its doing a full table scan causing the query to slowdown.I have tried creating index on nvl(a.c2,'31-dec-9999')
But the CBO won't use it.Anyway to create index on this col so that full table scan can be avoided?
Performance Tuning :: How Length Of Column Width Effects Index Performance
Sep 30, 2010How 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'.
Performance Tuning :: How Expensive (speed) Is Unique Versus Primary Key In Large Table
Aug 15, 2011I have two design alternatives and need to understand how expensive (speed) is one of them against the other for a medium size table (100K-200K records):
create table xyz
(
f1 number not null,
f2 varchar2(20) not null,
f3 number not null,
f4 varchar2(50),
[code]....
the idea is to optimize the design by using a PK instead of the 3 keys and there is a debate that searching a unique index field(2nd scenario) is of the same speed than searching a PK field (1st scenario).
SQL & PL/SQL :: Difference Of Unique And Range Scan
Mar 11, 2010diff of unique scan and range scan?
View 1 Replies View RelatedPerformance Tuning :: SQL Not Using Index From Application?
Jun 6, 2013We have a DELETE statement when coming from application is not using index but when run from Toad or SQLplus as same user uses index. Explain plan also shows using index.I did a query on v$sql below is the output of the query( I have attached the same as a txt file). All the stats are up to date and confirmed from the developer the variable B1 is using the same datatype as column MAXMKY.
SQL_TEXTSQL_ID DISK_READSOPTIMIZER_HASH_VALUE
DELETE LOTA WHERE MAXMKY=:B1 2g2prrp3z56ah19,099,1891,846,735,884
DELETE LOTA WHERE MAXMKY=:B1 2g2prrp3z56ah0 1,846,735,884
OPTIMIZER_COST HASH_VALUEPLAN_HASH_VALUE MODULEPARSING_SCHEMA_NAME
[code].....
Performance Tuning :: STOPKEY And Index Use
Nov 6, 2010I am working on a query for a feedback response system which is going to be targeted at the common case when the user only want the most recent 10-20 rows in the feedback table. My though is to create an index on the date column, do a sort in an inner query and rownum <= in an outer query. This works as I expect when I am only querying the main table (lookup by index with a stop key), but when I start joining the main table to attribute tables I end up with a full table scan of the main table with the stop key applied after all the joins are completed, the index is nowhere to be found.
CREATE TABLE attr1_tbl(attr1_id NUMBER NOT NULL, attr1 VARCHAR2(10) NOT NULL,
CONSTRAINT attr1_pk PRIMARY KEY (attr1_id));
CREATE TABLE attr2_tbl(attr2_id NUMBER NOT NULL, attr2 VARCHAR2(10) NOT NULL,
CONSTRAINT attr2_pk PRIMARY KEY (attr2_id));
CREATE TABLE attr3_tbl(attr3_id NUMBER NOT NULL, attr3 VARCHAR2(10) NOT NULL,
CONSTRAINT attr3_pk PRIMARY KEY (attr3_id));
[code]....
One thing I noticed was that when no data is selected from the attribute tables, even if they are joined in the query, the CBO throws them out of the plan and only accesses the main table. With the foreign keys this makes sense and really just disqualified my first thought that maybe I was missing a foreign key or not null constraint somewhere.
I also added the cardinality hint to overcome the chance that in my test case there was so little data that index access is not worth it.
Performance Tuning :: How To Create Index
Mar 30, 2013I am going through this scenario:
* 35 | ID TABLE ACCESS BY INDEX ROW | S_ORG_EXT | 3064K| 2472M| | 1 (0)| 00:00:01 |
| 36 | INDEX FULL SCAN | S_ORG_EXT_U1 | 14 | | | 1 (0)| 00:00:01 |
Predicate Information (identified by operation id):
---------------------------------------------------
35 - filter("T2"."ACCNT_FLG"<>'N' AND ("T2"."INT_ORG_FLG"<>'Y' OR "T2"."PRTNR_FLG"<>'N'))
This unselective index scan on step 36 of the explain is returning 14 rows but optimizer is selecting 3064 K rows from the table .
I tried creating combined index on all 3 columns mentioned in the predicates for 35th step , but that is not utilized .
how to index this whole expression ::--
(ACCNT_FLG<>'N' AND (INT_ORG_FLG<>'Y' OR PRTNR_FLG<>'N'))
Something like CREATE INDEX XYZ on table((ACCNT_FLG<>'N' AND (INT_ORG_FLG<>'Y' OR PRTNR_FLG<>'N')) compute statistics ;
Performance Tuning :: Index Creation?
Aug 9, 2010is there any way to reduce the index creation time.
in my case one index creation took 5 minute and there are 5 indexes , so it took 25 minutes.
Performance Tuning :: Index With IN Statement
Jan 18, 2012I have the following problem. When I used in the IN-Statement fixed values e.q. 197321,197322,197323 ..., the index i_tab2_index works fine (index range scan).
But when I used in the IN-Statement an Sub-Select, the index i_tab2_index doesn't work (fast full scan)!My scale indices and used Selects:
CREATE INDEX i_tab1_index ON tab1 ( datum, flag_inst );
CREATE INDEX i_tab2_index ON tab2 ( tab2Idx, kontro );
SELECT count(epidx) as rowAnz
FROM tab2
WHERE tab2Idx IN ( SELECT tab1IDX FROM tab1
WHERE datum BETWEEN '20120117' AND '20120117'
AND flag_inst = '1' )
AND kontro = '9876521'
[code]...
Performance Tuning :: Index Monitoring
Aug 26, 2010get all the unused index in the system , if i put this query in batch job and execute it every night upto one months and store its data in a table and after one months i can get all the used indexes and left would be our unused indexes.
select
distinct p.object_name c1
from
dba_hist_sql_plan p,
dba_hist_sqlstat s
[Code]....
Performance Tuning :: Proper Index Is Not Used
Oct 17, 2012I have a table whose size is 2.3 GB and there are two indexes on it. One index is based on a Date column whose size is 900 MB, and the Other index consists of 5 columns including the date column, and the size is almost 2GB. But when i query the table using the Date column, it is doing a range scan on the second index which is almost the same size as the table. why is it not using the first index? What steps should i take so that it uses the First index without passing hints.
View 4 Replies View RelatedPerformance Tuning :: Difference Between Index Rebuild And Index Rebuild Online?
Jan 10, 2011What is the difference between index rebuild and index rebuild online.
View 3 Replies View RelatedPerformance Tuning :: How To Use Index On (ON In MERGE Statement)
Apr 6, 2011mbr has 60,000 rows and member has 60,000 rows approx. two tables have indexes on ssn, and citi_no on them.
PK of mbr : mbr_id
PK of member : mbr_id
other columns are not PK, and have no index on it.
I'm wondering why the statment doesn't use index while ssn and citi_no have index.
MERGE INTO mbr t
USING (SELECT mbr_id,citi_no
FROM member) a
ON (t.ssn = a.citi_no)
WHEN MATCHED THEN
UPDATE SET t.asis_mbr_id = a.mbr_id
where t.ssn not in(select ssn from mbr group by ssn having count(*) > 1)
Performance Tuning :: Index On Foreign Keys?
Jul 22, 2010I have to create indexes on foreign key columns ,now if composite index is already there with foreign key column then that will work or i will have to create a single column index.
View 17 Replies View RelatedPerformance Tuning :: Clustering Factor In Index?
Dec 15, 2010I am just curious to know what is clustering factor in index and How is it impartant in a sql tuning perspective ?
View 3 Replies View RelatedPerformance Tuning :: How To Find Index To Rebuilt
Oct 3, 2011i am trying to find the index want to rebuild or not for that i have analyzed that index after that i don't know how to calculate the ration could any one steps to do calculate the following ratio
Run the ANALYZE INDEX command on the index to validate its structure and then calculate the ratio of LF_BLK_LEN/LF_BLK_LEN+BR_BLK_LEN and if it isn?t near 1.0 (i.e. greater than 0.7 or so) then the index should be rebuilt. Or if the ratio BR_BLK_LEN/ LF_BLK_LEN+BR_BLK_LEN is nearing 0.3.
Performance Tuning :: Join Condition In Index?
Mar 14, 2012For a hash join statement, is it beneficial to have the join condition objects in the index as well as the objects in the where clause?
View 19 Replies View RelatedPerformance Tuning :: Why Oracle Doesn't Use The Index
Dec 2, 2010I have a table "NEWS_COMMENT" like this:
Name Type
------- --------------
ID NUMBER(8)
USERID NUMBER(8)
SORT_TEXT VARCHAR2(100)
TEXT VARCHAR2(1000)
DATE DATE
VALID VARCHAR2(1)
CODNEW NUMBER(10)
The table has a normal index for the userid column.
There is a query that looks for the differents CODNEW for a USERID but allways the CODNEW has to be greater than 2248833
select codnew from news-comment where userid=2914655 and valid='N' and codnew>2248833
I have created a new index for this kind of querys
create index coment_new_IDX on news_comment
(CASE WHEN codnew >2248833 and valid='N' THEN userid ELSE NULL END )
but oracle doesn't use it. I have used a hint to force it but doesn't run.
