How to use bitmap index

when we will use bitmap index in oracle?

hi,
you can take a look this documents
http://dylanwan.wordpress.com/2008/02/01/bitmap-index-when-to-use-it/
http://www.oracle.com/technetwork/articles/sharma-indexes-093638.html
regards,

Similar Messages

How to use the index method for pathpoints object in illustrator through javascripts

hii...
am using Illustrator CS2 using javascripts...
how to use the index method for pathpoints object in illustrator through javascripts..

Hi, what are you trying to do with path points?
CarlosCanto

Can downloaded oracle9i Enterprise Edition use Bitmap index?

Hello there,
I have a downloaded Oracle9i Enterprise Edition. After I create some bitmap index on a partitioned table, I use the following sql statement to check the bitmap index:
select index_name, index_type, status from user_index;
It tells me that all the statuses of the bitmap indexes are "N/A" (Not availabe). Does that mean I can NOT use bitmap index in this downloaded Enterprise version?
If I must use bitmap indexes, what should I do?
Many thanks in advance!
-wendy

are you creating a local index on the partitioned table?

Peformance tuning of query using bitmap indexes

Hello guys
I just have a quick question about tuning the performance of sql query using bitmap indexes..
Currently, there are 2 tables, date and fact. Fact table has about 1 billion row and date dim has about 1 million. These 2 tables are joined by 2 columns:
Date.Dateid = Fact.snapshot.dates and Date.companyid = fact.companynumber
I have query that needs to be run as the following:
Select dates.dayofweek, dates,dates, fact.opened_amount from dates, facts
where Date.Dateid = Fact.snapshot.dates and Date.companyid = fact.companynumber and dates.dayofweek = 'monday'.
Currently this query is running forever. I think it is joining that takes a lot of time. I have created bitmap index on dayofweek column because it's low on distinctive rows. But it didn't seem to speed up with the performance..
I'd like to know what other indexes will be helpful for me.. I am thinking of creating another one for companynumber since it also have low distinctive records.
Currently the query is being generated by frontend tools like OBIEE so I can't change the sql nor can't I purge data or create smaller table, I have to what with what I have..
So please let me know your thoughts in terms of performance tunings.
Thanks

The explain plan is:
Row cost Bytes
Select statement optimizer 1 1
nested loops 1 1 299
partition list all 1 0 266
index full scan RD_T.PK_FACTS_SNPSH 1 0 266
TABLE ACCESS BY INDEX ROWID DATES_DIM 1 1 33
INDEX UNIQUE SCAN DATES_DIM_DATE 1 1
There is no changes nor wait states, but query is taking 18 mins to return results. When it does, it returns 1 billion rows, which is the same number of rows of the fact table....(strange?)That's not a bitmap plan. Plans using bitmaps should have steps indicating bitmap conversions; this plan is listing ordinary btree index access. The rows and bytes on the plan for the volume of data you suggested have to be incorrect. (1 row instead of 1B?????)
What version of the data base are you using?
What is your partition key?
Are the partioned table indexes global or local? Is the partition key part of the join columns, and is it indexed?
Analyze the tables and all indexes (use dbms_stats) and see if the statistics get better. If that doesn't work try the dynamic sampling hint (there is some overhead for this) to get statistics at runtime.
I have seen stats like the ones you listed appear in 10g myself.
Edited by: riedelme on Oct 30, 2009 10:37 AM

How to use secondry index

Hi Experts,
I have a requirement to improve the performance of report,So i got some select querys there non primery keys are used for table VBAK,VBAP,LIKP,LIPS so i want to create secondry index for that,Any one can help me for that means after create secondry index how to use that index in report and for create secondry index required any MANDT field or Not.
Thanks.

Hello Ram,
Before creating secondary index you need to know the below points.
1) Do not create more indices on table
2) What is the frequency of table access
3) You should not create too much columns(should be less than 120 characters)
4) Cant you use existing indices?
5) DML operation will be delayed if you create index
Before moving to Production system please consider below the points.
1) Ask BASIS to create index in DB level then move your DDIC transport which will be faster
2) While creating index if the DB size is like more than 500 GB then downtime is required
Regards,
Vadamalai A

How to maintain bitmap index on a large table in DW?

Hi all,
We have many tables which are constantly doing either FULL or INCREMENTAL loading.
And we have created many BITMAP indexes and several B*Tree index (caused by PRIMARY KEY or UNIQUE key constraints) on those tables.
So, what I want to know is, how to maintain those BITMAP (and B*Tree) indexes for different loading mode?
like, should I drop the index before the full load and re-create it after that?
and do nothing in INCREMENTAL loading? I am aware that it will take more time to load with indexes.
any links, books, articles or opinions would be highly appreciated.
Thanks

Just to reiterate, add to what Adam said. From Oracle Doc
http://download.oracle.com/docs/cd/E11882_01/server.112/e17120/indexes002.htm#CIHJIDJG
Unusable indexes
An unusable index is ignored by the optimizer and is not maintained by DML. One reason to make an index unusable is to improve bulk load performance. (Bulk loads go more quickly if the database does not need to maintain indexes when inserting rows.) Instead of dropping the index and later re-creating it, which requires you to recall the exact parameters of the CREATE INDEX statement, you can make the index unusable, and then rebuild it.
You can create an index in the unusable state, or you can mark an existing index or index partition unusable. In some cases the database may mark an index unusable, such as when a failure occurs while building the index. When one partition of a partitioned index is marked unusable, the other partitions of the index remain valid.
An unusable index or index partition must be rebuilt, or dropped and re-created, before it can be used. Truncating a table makes an unusable index valid.
Beginning with Oracle Database 11g Release 2, when you make an existing index unusable, its index segment is dropped.
The functionality of unusable indexes depends on the setting of the SKIP_UNUSABLE_INDEXES initialization parameter. When SKIP_UNUSABLE_INDEXES is TRUE (the default), then:
•DML statements against the table proceed, but unusable indexes are not maintained.
•DML statements terminate with an error if there are any unusable indexes that are used to enforce the UNIQUE constraint.
•For nonpartitioned indexes, the optimizer does not consider any unusable indexes when creating an access plan for SELECT statements. The only exception is when an index is explicitly specified with the INDEX() hint.
•For a partitioned index where one or more of the partitions are unusable, the optimizer does not consider the index if it cannot determine at query compilation time if any of the index partitions can be pruned. This is true for both partitioned and nonpartitioned tables. The only exception is when an index is explicitly specified with the INDEX() hint.
When SKIP_UNUSABLE_INDEXES is FALSE, then:
•If any unusable indexes or index partitions are present, any DML statements that would cause those indexes or index partitions to be updated are terminated with an error.
•For SELECT statements, if an unusable index or unusable index partition is present but the optimizer does not choose to use it for the access plan, the statement proceeds. However, if the optimizer does choose to use the unusable index or unusable index partition, the statement terminates with an error.
Incremental load really matters the volume and whether for new dats you just add new partitions or subpartitions . If my incremntal go all over place and/or if I am touching few thousand rows. Yes might want to keep the indexes valid and let Oracle maintain it. IF millions added or incremental data just added to new part/subpart . Keeping indexes unsable for those partitions/subpartitions and the rebuilding it later may yield better results.

Using Bitmap Index over db link.

I've a problem with the following query:
select count(*)
from TABLE_A@db_link TABLE_A, TABLE_B
where TABLE_A.ACCEPTTIME = TABLE_B.TIME_B
The above query is doing a full table scan (even after forcing index hints) on TABLE_A which has about 300M records.
TABLE_A is a local table while TABLE_B is remotely accesed using db_link.
There is a bitmap index created on the ACCEPT_TIME field of TABLE_A which is not used by the query. However when I fire this query:
Am I missing something here? How can I make the optimizer use the bitmap index on TABLE_A using remote db_link?
Here is the explain plan for the above query:
Operation     Object Name     Rows     Bytes     Cost     Object Node     In/Out     PStart     PStop
SELECT STATEMENT
Optimizer Mode=ALL_ROWS          1           2
SORT AGGREGATE          1      17
NESTED LOOPS          1      17      2
REMOTE     .COPY_STM     1      9      2
     STAG_PLMSPDB1.SMART.COM.PH     SERIAL
INDEX RANGE SCAN     SYSTEM.DIM_TIME_INDX1     1      8      0
Regards,
Raj

Here is a simple case to explain the problem more clearly:
1. dept: database1 (small table dimension with 4 rows)
2. emp: database2 (large table fact with 50K rows)
3. Table emp has bitmap index on column "deptno"
4. Both tables are analyzed with defualt values using DBMS_STATS.GATHER_TABLE AND INDEX STATS
5. DB Link db2 is created from database1 to database2
Observations:
a) On Database2 when the following query is issued:
select count(*) from emp@DATABASE1 emp, dept where emp.deptno = dept.deptno
It does not use the bitmap index.
b) On Database1 when the following query is issued:
select count(*) from emp emp, dept@DATABASE2 where emp.deptno = dept.deptno
It does use the bitmap index since it is available optimizer has this information locally.
My question is how can I make use of the statistics effectively, so that the optimizer knows it has to use the bitmap index present in the remote db.
Regards,
Raj

How to use cfloop index value as part of another variable

Hello,
I have a RATE form that first asks "how many rates will you
be adding?" that answer generates a series of form elements based
on the answer. You then have a form grid to populate, 3 values for
each rate (price, code, name).
This part works fine. The issue is now I need to INSERT the
values into the table, so I need to use the INDEX value of the
cfloop to recreate the amount (and names) of the fields in the
INSERT statement. How do I escape, or re-create the evaluated form
elements ( in which their count is #i# as the loop goes) when I
need to evaluate for #i# AND evaluate for #form.sku_i_name# at the
same pass?
I am passing, for example, #form.sku_2_Name# where that might
equal "Half Page". The number 2 in that variable was assigned
during the form creation by the current index of a cfloop. Since my
action (insert) page does not know how many (out of 50 possible)
sku's are coming, how do I use the skuCount (another hidden value
passed as well) to create a proper INSERT SQL command when I need
to eval the form element and the index at the same time?
Obviously #sku_#i#_Name# does not work, and #sku_i_Name# does
not either... I know this can be done, and that I am just doing it
wrong.
Thanks for any help!

bigbrain28 wrote:
> Thank You, cfsearching! I don't quite understand 100%
how it works
As all three of us indicated you use array notation for this
type of
requirement. In ColdFusion you can use array notation or dot
notation
to access structure data. Almost all data in ColdFusion is
now some
type of structure.
I.E. #Form['myField']# is the same as #Form.myField#.
The advantage is that with array notation you can do things
you can not
do with dot notation. You can reference elements that have
keys that
are illegal variable names such as one with a space.
I.E. #url['my field'] is allowed, #url.my field# would fail
or course.
And you can concatenate the key string as we did with your
example.
I.E. #Form['aString' & aVariable]#
There are many powerful things one can do with this
knowledge. One can
access record sets with array notations. This can allow for
very
sophisticated parsing of a record set.
I.E. #myQuery['column'][row]#
You can dynamical call a variable. Thus creating dynamic code
that does
not even need to know what variables exist until run time.
I.E. #variables[anyName]#
This just scratches the surface.

Simple SQL Query is not using Bitmap index

Hello to All,
We are having Oracle9i Database and using it for the datawarehouse purpose.
I have created the bitmap index on calledinfo column and I am running the following simple query which takes serveral hours to complete:
select * from ssp.ssp_2006_q4 where calledinfo='799992515f'
OR
select calledinfo from ssp.ssp_2006_q4 where calledinfo='799992515f'
I don't know why it is not using the bitmap index: Can anybody help me here?
Thanks in Advance
Hashim

I know why and everyone that has read Jonathan Lewis' book on the CBO knows why.
Why? Because the CBO thinks the cost of using your index will be higher than the cost of ignoring it.
To see what Oracle is thinking run an explain plan using DBMS_XPLAN for create the output and then rerun it with a hint forcing index usage.
It is a mistake to believe that an index will always make things better. Issues of cardinality, clustering factor, etc. are very important.
Post the explain plans if you have any questions about what they show:
http://www.psoug.org/reference/explain_plan.html

How to use an index

Hi,
Can someone tell me how can I use a index of row?
I want to see if any value is repeated in a column something like
declare
x number;
type my_table is table of number;
var_c1 my_table;
begin
for i in 1..6 loop
select round(dbms_random.value(1, 49),0) bulk collect into var_c1 from dual;
if var_c1(i) = var_c1(i).next then
dbms_output.put_line(var_c1(1));
end if;
end loop;
end;
thank you

I am sorry but I do not understand the question.
If you want to see if each row is unique just try and create a unique index on the column or select column_name, count(column_name) group by column_name order by 2 or something similar.
John
www.jhdba.wordpress.com

How to use Browsing Index

Hi, I want to speed up a search that return a large number of users. For what I understood I need to create a Browsing index. I've created a browsing index following instruction on the Admin manual, but I really don't understand how to use it ?
After creating the index (ldapmodify + vlvindex), are this index used by default if the search mach the vlvbase and vlvfilter ?
Thanx

Sorry I don't know why I don't see the [notes=u] in the access log but it seam the my vlv is not created at all.
When i run vlvindex I get the following error:
[18/Feb/2005:12:28:01 +0100] - userRoot: Indexing VLV: Sort SN
[18/Feb/2005:12:28:02 +0100] - userRoot: Indexed search unsuccessful, will perform unindexed search instead.
No vlv#.... files are created in the db directory, so I think no vlv index are created..

How to use search index created by jhindexer

Hi i have created a JavaHelp set using Docbook which works ok but the search doesnt work. I then discovered jhindexer and have sucessfully used it to create a directory called index containing the index (DOCs,DOCS.TAB etc) in the same directory as the html files but it still doesnt work.
I guess i have to modify one off my javaHelp files (jhelpidx.xml,jhelpset.hs) to point to this index but cant find any info on this.
Can anyne help me please.

place the snippet below into your HelpSet File (.hs), the helpset file should be in the same directory as the JavaHelpSearch folder where your index files are located. See the structure:
/foo.hs
/JavaHelpSearch/DOCS
/JavaHelpSearch/OFFSETS
---- snippet -----
<view>
<name>Search</name>
<label>Suche</label>
<type>javax.help.SearchView</type>
<data engine="com.sun.java.help.search.DefaultSearchEngine">JavaHelpSearch</data>
</view>
---- snippet -----
And read the supplied PDF documentation, because if you have problems with this, you will have even more problems with some more advanced stuff.

How to use secondary index

Hi abapers,
Iam creating secondary index for the database table MSEG. ....How to write select query for the secondary index that i have created..
Regards,
Ramya

how to create secondary index in tables
https://forums.sdn.sap.com/click.jspa?searchID=933015&messageID=2971112
Guidelines to create secondary index
https://forums.sdn.sap.com/click.jspa?searchID=933015&messageID=2009801
Secondary index;
http://help.sap.com/saphelp_47x200/helpdata/en/cf/21eb2d446011d189700000e8322d00/content.htm
this will definitely help you, dont forget to award points if found helpful

How does OWB deal with bitmap indexes when inserting?

How does OWB 9.2 deal with bitmap indexes on a fact table when records are inserted from a staging table? It seems to me that they are left on the table, while in the 9i Server manuals it says that one should not perform heavy DML in this case, because this slows down the inserts considerably and the indexes can get bloated. Should one define a premapping and postmapping process for removal and recreation of the bitmap indexes?
How handles OWB bitmap indexes in case of PEL and what action should one take then?
Jaap.

Hai Japp,
It depends on the volume of the data.
The best way is drop index in pre mapping process and recreate it in post mapping process.
You need to use EXECUTE IMMEDIATE command in the procedure to create or drop indexes.
e.g:
EXECUTE IMMEDIATE 'CREATE BITMAP INDEX INDX_BI_TABLE ON TABLE_NAME(COL_NAME)'
Regards,
Malli

Trying to make use of bitmap indexes

Hello!
I have a table that contains about 16 mill rows and each night about
60.000-70.000 rows are proccessed against the table so that part of the rows
is updated and another part is inserted.
The table contains three IDEAL columns for bitmap indexes the first of which
may have only two, the second three and the third four distinct values.
I was planning to change the index type on these columns to BITMAP but
Oracle doesnt recommend to build BITMAP indexes on heavily updated or inserted
columns.
So the only use of bitmap indexes turns out to be read-only tables.
From the other hand a sloution might be dropping indexes before the load and rebuilding them after the load has completed what can lead to often tablespace fragmentations.
So, the question is how can I use bitmap indexes in a case like this one?
What are wayouts?
Thank you very mcuh for the reply.

>
The table contains three IDEAL columns for bitmap indexes the first of which
may have only two, the second three and the third four distinct values.
Contrary to popular legend, and possibly contrary even to the manuals and Metalink, these columns are NOT necessarily ideal for bitmap indexes. Consider a query with:
col1 = '1_of_2'
and col2 = '1_of_3'
and col3 = '1_of_4'You have a total of 24 possible combinations. Given your 16M rows, this means that on average the optimizer will expect to collect about 670.000 rows spread across something like 100,000 to 130,000 blocks. Under these circumstances you may find that Oracle doesn't use the indexes anyway (unless you fool it by fiddling with parameters like the optimizer_index_cost_adj, and that's generally a bad idea) - and if the model is a reasonable description of the actual data it probably shouldn't use the indexes.
There are various special circumstance that might make the indexes effective for querying, though. (Note - at this point I'm not considering the impact on inserts, updates and deletes). The most obvious example is where all three columns each have at least one very repetitive value and all your queries are trying to find data for the remaining "rare" values. If this is the case then you need to index the columns and collect histograms on the columns so that the optimiser can model the data correctly; and then you may also need to modify your SQL to ensure that your queries against these columns always use literal values, not bind variables.
If some of your queries are supposed to return small amounts of data, there are various mechanisms you could use to do this efficiently. If your queries are always going to return large amounts of data, then there are other strategies that are likely to be more appropriate.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk

How to use bitmap index

Similar Messages

Maybe you are looking for