Similar Questions

• Index B-Tree

  Link: the tree of balanced research (B-Tree) in SQL databases

  The course of tree is a very efficient operation - so effective that I refer to it as the first power of indexing. It works almost instantly, even on a large data set. This is mainly because of the balance of the tree, which allows access to all elements with the same number of steps, and on the other hand because of the logarithmic growth of the depth of the tree. This means that the depth of the tree grows very slowly compared to the number of nodes. Index of the real world with millions of records have a depth of the tree of four or five. You rarely see a depth of the tree of six.

  Hi Experts,

  I posted a link on the index B-Tree. My question is, would it be possible to know the depth of the index tree in Oracle?

  -Suri ;-)

  Take a look at understanding index | Oracle FAQ, https://mwidlake.wordpress.com/2009/11/13/blevel-and-height-of-indexes/ or https://richardfoote.wordpress.com/2008/04/03/so-when-does-an-oracle-b-tree-index-increase-in-height-almost-grown/

• Index B-Tree for the numbers

  Hello
  
  If we create an index b-tree on table coloumn (ex: emp: name) it creates leafs on first name.
  
  As: sheet sheet sup A - Z A - M, N - Z new subleafs A - F, G - M N - Q, R - Z.
  
  If the first name is RAM it looks in this journal.
  
  If we create index b-tree on numerical column how leafs will create. Please let me know.
  
  Thank you!

  Oracle B - tree Index Internals:
  Reconstruction of the truth:

  By Richard Foote
  http://richardfoote.files.WordPress.com/2007/12/index-internals-rebuilding-the-truth.PDF
  http://www.dbafan.com/book/oracle_index_internals.PDF

  And:
  http://www.asktheoracle.NET/how-do-indexes-work-internally-in-Oracle.html
  http://www.orafaq.com/node/1403
  http://en.Wikipedia.org/wiki/B-tree
  http://en.Wikipedia.org/wiki/B%2B_tree

  Ok. I just many links. Now your question, how B-tree works for numbers. I think first of all I'm going to go through above links then, I will try to answer you good. (I know, there is no need of my answer, you would understand a lot before my post!)

  Concerning
  Girish Sharma

  Published by: Girish Sharma on January 29, 2012 11:36

• How to disable an index

  Hi all
  
  How to disable an index created by
  

  create indexes cc on sample (serialno);

  What are the index b-tree and bitmap in detail.
  
  What is a HASH function.
  
  What is a reverse index.
  
  Thank you and best regards,
  Sri ram.

  Some links:

  Look here as unusable, and reconstruction (take care of the restrictions, he also described):

  http://download.Oracle.com/docs/CD/B19306_01/server.102/b14200/statements_1008.htm#i2136020

  You can find a bit of information on the b-tree index here:
  http://download.Oracle.com/docs/CD/B19306_01/server.102/b14220/schema.htm#sthref961

  Index REVERSE button:
  http://download.Oracle.com/docs/CD/B19306_01/server.102/b14220/schema.htm#sthref998

  Bitmap-index:
  http://download.Oracle.com/docs/CD/B19306_01/server.102/b14220/schema.htm#sthref1008

• Tree B or Bit MAP

  Hello
  
  How do I know an index b-tree or bitmap index. I know the difference between these two indices. The way they work and other things. I don't know how to create them.
  
  What is the default index in oracle. How will I know if an already existing index is tree of type B or bitmap.
  
  What is oracle allows to select the type of index on the columns mentioned in the creation of the index.
  
  Thank you
  Rakesh

  Create the Index B-Tree:

  CREATE INDEX emp_dept_ind
  ON emp(dept)
  

  Create the Bitmap indexes:

  CREATE BITMAP INDEX emp_c1_bind
  ON emp(c1)
  

  With greetings
  Krystian Zieja
  http://www.projectenvision.com

  Published by: krystian.zieja on April 8, 2010 21:25

• B - Tree and explanation Index Bitmap

  Hi gurus

  I am trying to absorb the notion of bitmap index and b-tree, but unable to grasp the concept, so far, I have learned the following:

  Index B-Tree

  Use in the OLTP environment

  It is customary for these types of columns where you have more unique value or we can say that high cardinality

  It occupies less storage

  Using the corresponding model and ranges

  By default, Oracle uses tree indexing

  Bitmap index

  Use in home environment/OLAP data items

  It is customary for these types of columns where repeated values exist or we can say that low cardinality, example are male and female

  It seems that these points of difference between the two indexes. I really appreciate if someone give me more explanation on these subjects.

  Thanks in advance

  Concerning

  Muzz

  I am trying to absorb the concept index bitmap and tree but unable to grasp the concept,

  Then the FIRST place to look is the Oracle documentation; specifically the chapter "Index and Index-Organized Tables" chapter of the Concepts doc.

  http://docs.Oracle.com/CD/E25054_01/server.1111/e25789/indexiot.htm

  3 indices and Index of Tables

  This chapter deals with indices, which are schema objects that can speed up access to the lines of the table and organized index of tables, which are tables stored in an index structure.

  This chapter contains the following sections:

  • Overview of index
  • Overview of the Tables organized by Index

  This chapter has a lot of basic information on ALL the various types of indexes.

  so far, I've learned the following:

  Where, exactly, 'have you' who? Most of it is wrong, incomplete or distorted.

  Index B-Tree

  Use in the OLTP environment

  Index B-Tree, by default, are used in all environments.

  It is customary for these types of columns where you have more unique value or we can say that high cardinality

  They can be used for a cardinality. True - a unique column index is most commonly used for high-cardinality columns. But Oracle may also use an index column, simple or composite, when the data being sought is ENTIRELY contained in one or more indexes, low cardinality.

  It occupies less storage

  Maybe, maybe not. It is based on the column being indexed, the size of the key values and the cardinality of the key values. For your example "Male and female" there will be only THREE index entries: male, female and null. And each entry is simply a list of ranges of ROWID. This index can be orders of magnitude smaller than the equivalent B-Tree index.

  Using the corresponding model and ranges

  For the most part correct - although the range queries can be used with the bitmap index which is not a common use.

  By default, Oracle uses tree indexing

  Fix.

  Bitmap index

  Use in home environment/OLAP data items

  Especially correct - DML on tables with the bitmap index can cause severe performance and throughput problems. The distinction is therefore between environments with medium/high DML on a table compared to the weak or nonexistent DML on a table.

  So rather than a distinction between environments (OLAP and warehouse) the distinction is no longer between the TABLES (high/medium DML versus LOW/NO DML). There is nothing wrong at all with the help of the index of the bitmap in an OLAP environment - but these indices should be limited to the tables with low, or no, DML.

  It is customary for these types of columns where repeated values exist or we can say that low cardinality, example are male and female

  Yes and no.

  Yes - a bitmap index is not really appropriate, if there is NO repeat value.

  No - part II (low cardinality). The attribute MAJOR missing from what you have posted is that bitmap indexes are ALMOST always used in conjunction with others (usually a bitmap) index.

  If one, or more, high cardinality bitmap index can be used VERY effectively together to identify a set of rows to a query.

  See my multiple responses in this thread

  https://community.oracle.com/message/10219613?

  One of my answers presents, in detail, just how many attributes can be combined using several bitmap on both high columns index and low cardinality.

  In a later response, I provide the actual sample code and display the execution plan indicating how Oracle just that.

  SQL> set serveroutput on
SQL> set autotrace on explain
SQL> select rowid from star_fact where
  2   (state = 'CA') or (state = 'CO')
  3  and (age = 'young') and (marital_status = 'divorced')
  4  and (((summer_sport = 'baseball') and (softdrink = 'pepsi'))
  5  or ((summer_sport = 'golf') and (beer = 'coors')));


  Read the full thread.

• BTREE and Bitmap indexes

  How the Btree and Bitmap index works?

  Osama_mustafa wrote:
  If you google it you will find some topics/article talking about this.

  Refer to this:
  Index bitmap:
  http://www.DBA-Oracle.com/oracle_tips_bitmapped_indexes.htm

  BTREE index
  http://www.DBA-Oracle.com/t_garmany_easysql_btree_index.htm

  Better not to refer to one of these items, they contain too many errors.
  If textbooks are not good enough, then the best source of information indexing is Richard Foote's blog.

  (Or add "Richard Foote" for your research, you do it for the b-tree or bitmap index.

  Concerning
  Jonathan Lewis

• Index Bitmap and MV in Standard edition

  Salvation of DBA
  
  I have an enterprise edition 10.2.0.3 database which can be transformed into 11.2.0.3 EE. There many Materialized view with activated query rewrite. If I downgrade to the standard edition, what will be the impact? I know the rewrite of the query is a feature of EA and not SE and SEO. It is also the index Bitmap in the database which I think must be re-created as the normal b-tree index.
  
  I know that bitmap is not a feautre of the SE. One advantage that I see that updates will be faster if there is a normal index as DML are slow, if there is a Bitmap index.
  
  What will be the impact on the performance of the database if there is standard edition which does not rewrite of the query and the characteristics of Bitmap?
  
  Thank you
  
  DBA is the hero behind the screen, while developers are heroes on the screen.

  user13368428 wrote:
  I went through this table before posting my first post. I don't know there are a lot of tables in my EE database that contains bitmap indexes. In the past, I turned on the control over some of them, and they have been used. Also, I have seen queries that are rewritten to use the MV table instead of the base of fact tables.

  Yes. Really, I need to test in decommissioning and annexing the request to it. But I wanted to know if anyone has experienced this. What were their experiences do not use Bitmap indexes, function index and Query rewrite.

  Your response was very useful.

  Thank you.

  The Oracle Server Standard edition supports function based indexes (I think since version 8.1.5). Bitmap indexes are not supported and treat B * index of tree as the index of the bitmap to bitmap join operations are also not supported. You can partially determine the impact of not having the second option by editing a hidden at the session level setting (obvious caveat on masked editing settings apply here):

  ALTER SESSION SET "_B_TREE_BITMAP_PLANS" = FALSE;
  

  I'm fairly certain that the Standard Edition supports materialized views - automatic query simply not rewrite for possibly enjoy this feature based on cost.

  There may be a few other surprises, here is part 1 of 4 that explores the potentially unexpected differences between Standard Edition and Enterprise Edition (the differences are version and OPTIMIZER_FEATURES_ENABLED load):
  http://hoopercharles.WordPress.com/2010/11/21/different-performance-from-Standard-Edition-and-Enterprise-Edition-1/

  Good luck to you with the project.

  Charles Hooper
  http://hoopercharles.WordPress.com/
  IT Manager/Oracle DBA
  K & M-making Machine, Inc.

• Bitmap index Btree n

  diff bet index bitmap and btree, how his work... ??

  1 index B-tree has low cardinality values, whereas Bitmap Index offers high cardinality values.
  2. other than the way in which they put in place, one of the functional difference is Bitmap indexes can index null values where as BTREE index cannot.
  3 updates tree index on keys was relatively inexpensive, where as a Bitmap index more expensive

• Question index bitmap

  Guys,
  
  I have a general question about the bitmap index. I develop a data model for a new system.
  
  I have a table that will get close to 20,000 files per year. There are 4 broad categories, and each row in this table is covered by one of these 4 categories. I'll use the category several times field to search all the records in the system.
  
  Don't you think that a Bitmap index on the category column will be a great help? A comment I received from my internal staff member is that: Bitmap can be an overkill for this kind of small table
  
  All comments or suggestions would be a great help...
  
  -Raj

  Hello

  I see no points you must have an index on that column bitmap if you encounter one single index bitmap for this table. Other columns are also a good candidate for the bitmap index?

  For such a small record 20,000 per year (assuming that the size of each line is normal) and with four distinct values, I doubt that you will get no gain performance between full table scan and bitmap.

  Even with 20,000 lines and four distinct values and are filled at the same time that you create a tree index b top as the grouping factor is very low. Still, he would not give a lot of benefits.

  And if most of the research is run on this table, I see it as a good candidate to keep bool in the buffer cache.

  Concerning
  Anurag

• Index of bitmap in OLTP

  Hi all
  
  I'm working on OLTP system and most of the operating table has less then 1 million documents. Some fields have very low cardinality as contract type and status value. My question is, it is advisable to create Bitmap indexes on such type of columns in OLTP system or should I go for normal index?
  
  Thank you
  Danish

  In fact, there a lot of research on the Type of contract and the State, which must therefore the problem in creating Index Normal in this case?

  Some fields have very low cardinality

  Index B-Tree are best used for high-cardinality columns / combinations of columns.

• create b-tree indexes in SSD

  Hello
  in the Data Warehouse database, can I create tree b index on the customer_id in the table customers-> very high cardinality
  
  or because it is MAS is much better as the Bitmap index (even if it's high cardinality)
  
  Thank you very much

  Yes, you can create an index b-tree normal, on any column in your table, regardless of the cardinality. If it will be used by the optimizer for a given SQL query is another problem. It will probably not be used in the usual way, you wait, but could be used to Index the Fast scan in some queries if it was cheaper than alternatives.

  Instead, you can create a bitmap index as you say, but know that bitmap indexes be locked during inserts. So they should not be used in environments OLTP concurrent transactions, or where you want to bulk load with the parallel flow data.

  Anyway if I were in your shoes I would experiment with both. What problem are you trying to solve anyway? Just creating indexes for the good of them is not that constructive. A bitmap index is not very useful in itself. Bitmap indexes are intended to be used in combination with other clues bitmap on the same table, to determine which rows of data meet several conditions in a complex query. While you have the other index bitmap on this table? Already using part index bitmap of your strategy?

  I find it always better to work forward to a problem to a solution. That's why I asked if you had a problem that you tried to resolve with this index. Working backward is literally invent a solution and there is a problem it needs hope. And often, this can be a waste of your time, that is, there is no problem that must be solved.

  John

• index bitmap and separate key

  Hi guys,.
  
  If the separate keys is very low (for example 20) and my index finger has more than 12,000 lines, should I consider using a bitmap index instead?
  
  Thank you

  OracleGuy777 wrote:
  But that say our table was very fragmented, would not--what it means that the bitmap index entries would be to store much more information than necessary? Say so we had a table with only 1000 entries and the first rowid is 1, and the last was 1000000 and then eventually we have 999000 additional entries for each bitmap index entry!

  Bitmap indexes are well compressed. So, this usually isn't a problem. An example...

  SQL> create table t as select rownum id from dual connect by level <= 1000000;
  
  SQL> execute dbms_stats.gather_table_stats(user,'t')
  
  SQL> select blocks from user_tables where table_name = 'T';
  
      BLOCKS
  ----------
        1557
  
  SQL> delete t where id between 500 and 999500;
  
  999001 rows deleted.
  
  SQL> commit;
  
  SQL> create bitmap index i on t (id);
  
  SQL> select distinct_keys, blevel, leaf_blocks from user_indexes where index_name = 'I';
  
  DISTINCT_KEYS     BLEVEL LEAF_BLOCKS
  ------------- ---------- -----------
            999          1           4
  

  Notice how the index has only 4 blocks of leaves...

  So you're saying something like

  FEMALE 1 0 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 0 0 0 1

  could be stored as

  FEMALE 1 0 0 0 1 1 0 1 0 1 for rowid a to j
  FEMALE 0 1 1 1 1 0 0 1 0 0 0 1 for rowid k - w

  Yes.

  HTH
  Chris Antognini

  Troubleshooting Oracle, Apress 2008 performance
  http://top.Antognini.ch

• Clustering factor vary for each index?

  Dear experts,

  Today when I was reading an article on bitmap indexes and index b-tree, I learned something new called consolidation factor. I read more about this and I was wondering which makes him change for each index?

  For example, lets say that I had the table as follows

  create table emp)

  emp_no number primary key,

  name varchar2 (50).

  name varchar2 (50)

  );

  create index emp_name_indx on emp (name);

  We got two indexed columns, one is emp_no and the other's name. My question is, suppose that we have inserted some 100 million lines with a sequential order by emp_no. However, the names may be different. for example;

  1 michael jackson

  2 toni blair

  Zack 3-wire

  ......

  mike tyson 1000000

  I mean, the names are scattered. And I think it's quite normal because you can only insert a command. So anyway, the factor of grouping of emp_no perhaps is low. However, for the name, it could be so high.

  If this is true, then it does not depend on us? We cannot do something to this factor, right? Because we can only insert rows based on the order of a column, isn't?

  My last question is also very important, lets say that we got 20 tables and these tables are filled with ascending order with hundreds of millions of rows. The factor of clustering for each index in these tables are also very high. Because the tables are filled with a sequential order and if the lines are added sequentially in the same blocks of data, i.e. the tables become widely dispersed in the data files. It's very bad for clustering factor?

  Thanks in advance.

  NightWing wrote:

  My last question is also very important, lets say that we got 20 tables and these tables are filled with ascending order with hundreds of millions of rows. The factor of clustering for each index in these tables are also very high. Because the tables are filled with a sequential order and if the lines are added sequentially in the same blocks of data, i.e. the tables become widely dispersed in the data files. It's very bad for clustering factor?

  See link below:

  Ask Tom & quot; Dba_indexes & quot;

  i.e. If you want CF to close the index of number of blocks, you must insert the data in the indexed column command; before the block insertion, you must inform this column order that is most important to you / indexed column.

  In the link above, Tom gave two examples:

  1 insert in... created id column order of indexes on columns id and name, so SEE the index for the id column is about the number of blocks. Because the order of column is the main factor for CF.

  2. Insert in... created name column order of indexes on columns id and name, so SEE the index for the column name is close to the number of blocks.  Because the order of column is the main factor for CF.

  Concerning

  Girish Sharma

• for bitmap or not...

  First of all, I would like to apologize if this question has been answered, but I couldn't find the answer to my related question.

  I am running 11.2.0.2 EE on Solaris 10.

  My problem is that we have a table very heavily used in an OLTP database that includes the columns that are regularly used in queries.

  These columns have very low cardinality and seem to be an ideal candidate for the bitmap index.

  But since we have so much activity on this table, I fear that it will be counterproductive on inserts and updates.

  I guess I also need to rebuild the IMC every night with the volume of business that we have on the table.

  The table is not a huge table and has only about 5 M record.

  We have also a history table that regularly has about 25 M records and would probably also benefit by having a BMI, but again, I have fear of the impact of BMI is when large jobs making insertions are made on the history table.

  Any ideas how to weigh whether it would be beneficial or not having the BMI is on the main table?

  I can test the use of BMI in our test database, but I can't simulate the normal load of users on the table to determine the impact of the performance.

  Your thoughts are appreciated.

  Bitmap indexes are not suitable for tables that have a large number of small insertions, deletions or changes that change the indexed columns - so your main table of 5 M of lines is not a good candidate.  However, OLTP systems tend to have queries more predictable than DSS or DWH, if the fact that you have a lot of columns 'low cardinality' (i.e. columns with a relatively important lines by the key value) may not be a problem if you can identify a few multi-column indexes and build them with compression on the main columns.  It is also interesting to note that even if you create the index b-tree on individual columns (even once, you would use compression), the optimizer can do "tree / conversion of bitmap" to optimize the use of these indices.

  History with 25 M lines table may be a better candidate if all what you do is inserts block with large table sizes - it can be done effectively, even when you have the index bitmap in place - and you can see that with a sufficiently broad framework for PCTFREE (eventually 51) when you initially create the index the index to stay in some sort of constant of size - only more in line with the evolution of the data.  If you are unlucky, you can find some of them unreasonably expanding quickly, then you can end up doing a daily load with a weekly reconstruction (for example).

  Concerning

  Jonathan Lewis

  http://jonathanlewis.WordPress.com

  Now on Twitter: @jloracle