Performance Tuning :: Materialized View With Nullable Column
Dec 29, 2011
I have an issue in materialized view which has got one of the null able column and query on this column taking approximately 2 mins where as other indexed columns takes less than 10 sec.
Here is the summary
SQL> Select Count (1), Count (VAT_NO) From Mv_customer;
If an index is created on VAT_NO will that improve the performance. What kind of index can be created considering very less number of records has got VAT_NO
I came across situation where a Nullable column is not using index for 'order by' clause. I added Not Null condition in the 'where' condition but it wasn't useful. I don't wanted to make composite index with not nullable column or with constant or modify column to 'Not Null'
So I carried out test cases and during which I found that in one case the sql statement does 'fast full scan' for data access but does not use index for 'order by' sorting
here are the steps
Initially I kept the column Nullable
SQL> create sequence s5; Sequence created.
SQL> create table t5 as select s5.nextval id,a.* from dba_objects a where rownum<1001; Table created.
SQL> set pages 100 SQL> select column_name,nullable from user_tab_columns where table_name='T5';
Misses in library cache during parse: 1 Optimizer mode: ALL_ROWS Parsing user id: 5
Rows Row Source Operation ------- --------------------------------------------------- 1000 SORT ORDER BY (cr=16 pr=0 pw=0 time=4771 us) 1000 TABLE ACCESS FULL T5 (cr=16 pr=0 pw=0 time=1157 us)
Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 68 0.00 0.00 SQL*Net message from client 68 49.49 49.72 ********************************************************************************
select /*+ index(t i5) */ * from t5 t where id is not null order by id
Misses in library cache during parse: 1 Optimizer mode: ALL_ROWS Parsing user id: 5
Rows Row Source Operation ------- --------------------------------------------------- 1000 TABLE ACCESS BY INDEX ROWID T5 (cr=150 pr=0 pw=0 time=5167 us) 1000 INDEX FULL SCAN I5 (cr=71 pr=0 pw=0 time=3141 us)(object id 4673065)
Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 69 0.00 0.00 SQL*Net message from client 69 22.89 28.04
Now I modified the 'id' column to Not Null
SQL> alter table t5 modify id not null;
SQL> set pages 100 SQL> select column_name,nullable from user_tab_columns where table_name='T5';
COLUMN_NAME N ------------------------------ - ID N OWNER Y OBJECT_NAME Y SUBOBJECT_NAME Y OBJECT_ID Y DATA_OBJECT_ID Y OBJECT_TYPE Y CREATED Y LAST_DDL_TIME Y TIMESTAMP Y STATUS Y TEMPORARY Y GENERATED Y SECONDARY Y
Misses in library cache during parse: 1 Optimizer mode: ALL_ROWS Parsing user id: 5
Rows Row Source Operation ------- --------------------------------------------------- 1000 SORT ORDER BY (cr=16 pr=0 pw=0 time=2398 us) 1000 TABLE ACCESS FULL T5 (cr=16 pr=0 pw=0 time=1152 us)
Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 68 0.00 0.00 SQL*Net message from client 68 37.74 37.91 ********************************************************************************
Misses in library cache during parse: 1 Optimizer mode: ALL_ROWS Parsing user id: 5
Rows Row Source Operation ------- --------------------------------------------------- 1000 TABLE ACCESS BY INDEX ROWID T5 (cr=150 pr=0 pw=0 time=4166 us) 1000 INDEX FULL SCAN I5 (cr=71 pr=0 pw=0 time=3142 us)(object id 4673065)
Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 68 0.00 0.00 SQL*Net message from client 68 8.28 8.45
Misses in library cache during parse: 1 Optimizer mode: ALL_ROWS Parsing user id: 5
Rows Row Source Operation ------- --------------------------------------------------- 1000 SORT ORDER BY (cr=6 pr=0 pw=0 time=1342 us) 1000 INDEX FAST FULL SCAN I5 (cr=6 pr=0 pw=0 time=1093 us)(object id 4673065)
Elapsed times include waiting on following events: Event waited on Times Max. Wait Total Waited ---------------------------------------- Waited ---------- ------------ SQL*Net message to client 68 0.00 0.00 SQL*Net message from client 68 1.88 1.89
Questions are
1) Why adding 'where id is not null wasn't enough for the index to get used in 'order by'? 2) While we got 'fast full scan' why index wasn't used for 'order by' clause? 3) Do we need the indexed column in where clause for being used in 'order by clause' too? 4) Do we need 'order by' clause if we are selecting only the indexed column with sequence generated values?
I have created a materialized view and also a normal View, which has 3 tables used in both the views, when inserted new records it reflects in a normal view but when i select the materialized view i cant see the updated data.
here is the materialized view i created;
CREATE MATERIALIZED VIEW pct_sales_materialized BUILD IMMEDIATE REFRESH ON DEMAND ENABLE QUERY REWRITE AS SELECT A.DEP_NAME,B.EMP_ID,C.EMP_NAME FROM department_head A,department_child B,emp_detail C WHERE A.DEP_ID = B.DEP_ID AND B.EMP_ID = C.EMP_ID
In search queries generally we select 10-25 columns (more can't be displayed on the screen) from 5-10 tables
Say in case of insurance related application, the search might be on policy number, policy holder's first name, policy holder's last name, region, policy type etc.
And not to many columns we are displaying on the screen, say, 4 tables have collectively 4 * 20 = 80 columns, then we are displaying say 12-15 columns with 2-3 columns have aggregates on it.
since the search criteria (e.g. first name, last name, policy number etc.) is not known till last moment it will be a generic dynamic query
Is it possible that instead we create a Materialized view with query with only joining conditions but no filter conditions and selecting only columns to be displayed on the screen and then we will refresh the materialized view (to take care of recent business transactions) and fire refined query with filter criteria on this materialized view
Select col1,col2,col3,col4,col5 From tab1,tab2,tab3,tab4 Where tab1.col1=tab2.col1 And tab2.col2=tab3.col2 And tab2.col2=tab4.col2;
Will it improve performance of the search functionality
I have a base table with ~20 mio. records with two FAST REFRESH Materialized Views based on that table using various aggregate functions in their view definition.
The problem is, when e.g. one record changes in the base table, I see two records in the MV log table MLOG$, but invoking the fast refresh mechanism by using using:
1) TXN_HD_FCT (This table has 6 billion records. Has fields TXN_DT, CUST_ID, TXN_AMT, TXN_ID and the table is partitioned on TXN_DT. We load data approximately 600K+ records to this table every day 2) RELINK_CUST (This table has 2 fieds CUST_ID and NEW_CUST_ID). We load data approximatley 100-200K+ records every day into this table. This table has total 10MM+ records now.
Now i need to create a table (TXN_UPD_HDR_FCT) in Schema B by joining above 2 tables using below query every day
CREATE TABLE TXN_UPD_HDR_FCT select a.TXN_DT, nvl(b.new_cust_id, a.cust_id) as cust_id, a.txn_amt, a.txn_id, from schema_A.TXN_HD_FCT a, schema_A.RELINK_CUST b where a.cust_id = b.cust_id(+);
We update CUST_ID to NEW_CUST_ID based on some rules (and keep it in the table RELINK_CUST) and need to take this new_cust_id while building the table TXN_UPD_HDR_FCT.
Building this table is taking approximately 4+ hours every day. just refresh only records from TXN_HDR_FCT whose CUST_ID is changed or any records inserted into TXN_HDR_FCT? I read about Materialized views but not sure how can i create MV logs on 2 tables? If i use materialized views do i need to create indexes every day?
We are using the below query to create a Materialized View but it has been running since 3 hours. It is an Oracle 9i database running in HP-UX.The quey is as follows,
(SELECT /*+ use_nl(A) parallel (A,4)*/ A.ICD_CODE AS ICD_CODE, A.ICD_DESC AS ICD_DESC, A.PROC_GROUP as PROC_GROUP, B.COMPL_ICD_CODE AS COMPL_ICD_CODE, B.COMPL_GRP_TXT AS COMPL_GRP_TXT, C.PROC_TYPE AS PROC_TYPE , [code]....
I need to create a materialized view with a clob column based on a varchar2 column of a table.This is because in the mv the clob column data gets appended one after another.
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 view, below, which does few left outer joins to the same V_MARKET view to get data i need. When I run SQL by itself, ut runs pretty fast, 2-5 seconds. But when I do "select * from V_DEPT_DATA where busines_date = '01-APR-10'", it takes more than 10 minutes to run. I added all needed indexes and still have problems with it .
CREATE OR REPLACE VIEW V_DEPT_DATA AS SELECT v1.business_date , v1.division , v1.department , v1.account , en.trader , [code]........
I have a view on base tables holding historical data for previous 60 months(one table per month) with union all operators.create index on those base tables will improve performance or creating a primary key with disabled novalidate will improve for retrieving data?
The view has around 8 million data and used as a fact table with 4 dimension tables.A DTS package from MSSql side refreshes OLAP cube by retrieving data from these tables in oracle.
If you have 3 tables (yr09, yr10,yr11) one with 2009 data, 2010 and 2011 data respectively. And a view (vw_yr091011) with a "union all" on all three.
Question: Will the performance be same for the following two queries ?
Question: Will Oracle read all 3 tables in the view when we search for only one year ?
select count(*) from yr09 where year = 2009;
-- vs
select count(*) from vw_yr091011 where year = 2009;
The following link says yes, the performance remains the same.
Link: [URL]..........
when I tried on a volume of 14000 records. The count came out same but the view took 50 more sec. And the explain plan shows it accessed all three tables.
base on performance it is better to retrieve data from view or mention the table names directly?
I have a select statement in from clause one of my table is view (which is having data collected from four tables) my question is whether performance of querry will be improved if i use directly all tables( four tables of a view) instead of a view
Now we are supposed to apply column level TDE to some of our table in database. Now it will be a 'ALTER' on the columns. it involves 4 big tables out of which 3 tables having size ~30GB(one is partitioned table) and another one ~800GB(Not partitioned) Now the concern is, what will be the efficient/safest way to apply TDE on columns, below are the two options with us. (NOTE - We do have downtime window during DB maintenance but looking at the size of the table, i suspect it might take lot.)
1. Directly apply 'ALTER' on the columns. (Note- i was testing on my local, it took 3hrs for a 30GB table to ALTER the column to TDE)
2. Use Table Redefinition for Altering the column. (Creating interim table with column as TDE and then Redefining whole table).
SELECT CURRENTSTEP FROM (SELECT ( WFENTRY.NAME || ',' || CURRENTSTEP.STEP_ID ) AS CURRENTSTEP, (CASE WHEN WFENTRY.NAME IN
[Code]...
in this query I am concatenating tow columns , I use this query as a sub query in my other queries and filter the results with and CURRENTSTEP = ?
here is how I use it
select sys_audit_id from ( SELECT * FROM (SELECT F.FINDING_NUMBER,
[Code]....
I saw adding this as a subquery with the filter and CURRENTSTEP = ? is slowing my query very much , as this is a derived column i cannot add index then how to improve performance for this subquery ?
We have a table called address and having the address fields and city ,state etc. The table will store huge amount of data .We need to query on the table. I would like to know how can we fasten the query and improve the performance of the query by creating index on these columns...Query is given below . note that the nullable columns can have data
I'm trying to collect histograms for column COL_C of table TAB_A(150K records), So an index "BAD_IDX" will *not* be used in a query when the value is not selective.
This is my query:
SELECT COL_A, COL_B , COL_C , COL_D , COL_E , COL_F FROM TAB_A WHERE COL_A = 050 AND COL_B = 13012345 AND COL_C = 0 AND COL_D = 0 AND COL_D >= '07/23/2013 00:00:00' ORDER BY COL_E ASC;
Now, I have index "BAD_IDX" on columns (COL_C, COL_E ).and the distribution of values looks like this:
select COL_C, count(*) FROM TAB_A --very not selective for 0, selective for the rest, also no histogram group by rollup(COL_C) order by 2 desc;
and the result is 20k row long (20k distincts), So I'll post just the top part of it:
Now, the problem with the query was that "COL_B = 13012345" was the most selective predicate, And an index for it did not exist, so the index "BAD_IDX" is used, and is scanning 86k records (all the "0" value records for column COL_C)!
So, I created an index
Create index GOOD_IDX on TAB_A(COL_B) compute statistics;
However, that BAD_IDX index is still being used! I've thought that maybe it's because the lack of histograms for the column COL_C.I've also understood from documentation I've read that the suitable histogram type is TOP FREQUENCY, Because although I have 20k distincts here for the column COL_C, what does the difference is the 86k records of value 0.
select distinct S.ID ID from ods.hso_Scheduled H, ods.SO_SCHEDULED S where S.insertion_date >= to_date('01-DEC-2011') and S.insertion_date < to_date('01-FEB-2012') and H.ID=S.ID
Both the involved tables, HSO_SCHEDULED is having 15 million records and SO_SCHEDULED table is having 7 million records.
I have created following indexes on these tables:
Indexes on SO_SCHEDULED: Index name Column name SS_IDX1ID, SO_SUB_ITEM__ID SS_IDX2INSERTION_DATE SS_IDX3ID, INSERTION_DATE SS_IDX4ID, SO_SUB_ITEM__ID, INSERTION_DATE SO_SCHEDULED_ID_PKID
I'm trying to create a Materialized View on a remote database from a simple view. The reason is, the data owners don't want to grant explicit tables privileges to external subscribers.
A new schema is created to publish data in the form of a view. I've created mlogs on the master tables, and granted them to the subscriber, but it's still complaining about a missing primary key on the view. A primary key does exist in the master table.
Is there another work around for this situation without having to work inside the data sources' environment?
I am facing some challenge while running update query on newly added column in existing table.
Environment Details Oracle 9i, version 9.2.0.6 Os Unix Aix 6.1
No of records in table : 12572770
Below are the step i followed.
1. In table testtablename, I have added new column COLUMNNAME29 with datatype VARCHAR2(8). 2. After adding the new column, i executed the update query to populate the data form COLUMNNAME1 to COLUMNNAME29. 3. The query is executed using COLUMNNAME24 in where clause, to drive query in index based.
SQL> desc testtablename Name Null? Type ----------------------------------------- -------- ---------------------------- COLUMNNAME1 VARCHAR2(8) COLUMNNAME2 CHAR(1) COLUMNNAME3 CHAR(1) COLUMNNAME4 VARCHAR2(8) COLUMNNAME5 VARCHAR2(11)
[Code]...
Table altered.
SQL> select index_name, column_position, column_name from dba_ind_columns where table_name = 'TESTTABLENAME' order by index_name,column_position;
1. The update query is hanging in database, it's not progressing (In single update, approximately 40000 records will get update) 2. No oracle error thrown in alert log or in session where the query being executed. 3. The event for the query is "db file sequential read". 4. When i update the newly added column COLUMNNAME29 with static value "1", the update completed successfully in few seconds. 5. Then i changed the static value to "1111" and executed the update statement, which result to query hanging in database. 6. I tried to update the existing column(COLUMNNAME1) in table with static value "1111", the update completed successfully.
Below are the queries completed successfully
Update Testtablename Set Columnname29 = '1' Where Columnname24 >= To_Date('01-12-2002 00:00:00', 'DD-MM-YYYY HH24:MI:SS' ) And Columnname24 < To_Date('01-01-2003 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
[Code]...
Below are the queries hanging in database
Update Testtablename
Set Columnname29 = Columnname1 Where Columnname24 >= To_Date('01-12-2002 00:00:00', 'DD-MM-YYYY HH24:MI:SS' ) And Columnname24 < To_Date('01-01-2003 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
Update Testtablename
Set Columnname29 = '1111' Where Columnname24 >= To_Date('01-12-2002 00:00:00', 'DD-MM-YYYY HH24:MI:SS' ) And Columnname24 < To_Date('01-01-2003 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
Below is character set in database
SQL> select * from v$nls_parameters; PARAMETER VALUE ---------------------------------------------------------------- ---------------------------------------------------------------- NLS_LANGUAGE AMERICAN NLS_TERRITORY AMERICA NLS_CURRENCY $ NLS_ISO_CURRENCY AMERICA
I have a materialized view "pro_mview",I am trying to refresh the MVIEW by using the following statement.
EXEC DBMS_MVIEW.REFRESH('pro_mview','C');
But I am getting the below error.
* Error at line 1: ORA-12008: error in materialized view refresh path ORA-00942: table or view does not exist ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2256 ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2462 ORA-06512: at "SYS.DBMS_SNAPSHOT", line 2431 ORA-06512: at line 1
I am able to fetch the data from that materialized view(pro_mview).
what would be the difference between a view and a materialized view? whether DML possible on a view? i think error occurs if DML tried on a view which is a combination of two or more tables, whether DML possible on a materialized view?
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?
I have requirement to create materialized views. The design states to use Complete refresh. Now I am using WITH ROW_ID clause.
1. Question - what are the criteria to decide between WITH PRIMARY KEY & WITH ROW_ID clauses? I referred oracle doc, but couldn't exactly get this.
2. Background - The oracle doc mentions that - Primary key materialized views are the default type of materialized view. The master table must contain an enabled primary key constraint, and the defining query of the materialized view must specify all of the primary key columns directly.
Question - I saw some existing materialized views in my project using WITH PRIMARY KEY clause, but all of the primary key columns are not part of the Select query, but still these views are working fine, how is this possible?
3. Background - The oracle doc mentions that - Rowid materialized views must be based on a single table and cannot contain any of the following:
■Distinct or aggregate functions ■GROUP BY or CONNECT BY clauses ■Subqueries ■Joins ■Set operations
Question - But I have created a Rowid materialized view selecting data from more than one table & defining query involving outer joins. This materialized view got created & getting refreshed (complete refresh). But again this is contradicting with Oracle' statement.
