Similar Questions

• 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.

• Bitmap index frequently updated useful column or not?

  I have a table of transaction with the status column.

  Table contains millions of records.

  Status, column values can be hold, dealt with, consult, error, completed.

  Initially table column populate status pending and later value will be updated to processed or see even then will be updated to completed or error.

  Is it useful to have the index bitmap on this column we update frequently on the status value

  Is it useful to have the index bitmap on this column we update frequently on the status value

  No - your is NOT a valid use for a bitmap index case.

  There would be little or NO value with only one index of bitmap on the table, if the column has been updated frequently or not.

  The power of the bitmap index is stronger when MULTIPLE indexes are used in the same query to identify/filter data.

  See my answers in this thread

  https://forums.Oracle.com/forums/thread.jspa?MessageID=10217613�

  In this thread I provide more details and code examples and execution of plan that show you a more typical use of bitmap indexes and their power.

  Try this code example to get a better understanding of the proper use of the case for the bitmap index.

• When the CBO would not use bitmap indexes available?

  I have a large data warehouse table in a star schema classic, with an index number of bitmap for the dimension tables. When you run queries that contain parameters for multiple indexes, the CBO will only use generally one or rarely two bitmap index.

  It seems to me that if the indexes are valid, statistics, the values of the parameters are present, etc and the CBO uses a bitmap index in an AND condition, he would like to use all those she could.

  there all the parameters that affect or bitmap how indexes him CBO will use? I'm looking for some advice on what to look for or research.

  Database is 11.2.0.3 base with no patch.

  Thanks in advance,

  Sean

  rp0428 - who has been deliberate because my question is not "how to solve this problem", that's exactly what I pointed out in my post. Just trying to see if there are all the controls to weight the decision-making community organizations in this area.

  OK - then let me simply state it.

  No - there are NO these parameters. But most of the posters are not really looking for a simple yes/no answer even if of many word of questions like that.

  See my response as of March 18, 2012 19:21 in this thread: https://community.oracle.com/message/10219613?

  Here I provide a simple table with SIX bitmap index, a query that uses predicates that combine values since the execution plan and the six columns indicating the different INDEX of BITMAP UNIQUE BITMAP, BITMAP or operations and BITMAP CONVERSION to ROWID.

  I won't repeat everything here, but this example should show you that Oracle will limit itself the way you suggest.

• Index bitmap for FKs on fact tables

  Hi all
  
  We have a database of DWH (Star Dimesions and the tables schema) running with OBIEE 11 g (11.1.1.1.6) on the oracle 11 g (11.2.0.1) database. I read in one of the best practical paper, creating index Bitmap on the Fks of all fact tables will help performance.
  
  I created indexes for the less than 2500 separate keys, but we have 2 dimesions tables where there are great number of records (size 14 g and 10 g). Can I go ahead and create indexes of bitmap for 2 tables establishments (mainly account_key and customer_keys are the columns)?
  
  Worried about creating index bitmap for large tables where they could affect the ETL process.
  
  Ref: http://www.oracle.com/technetwork/database/bi-datawarehousing/twp-dw-best-practies-11g11-2008-09-132076.pdf (page 20)
  
  Help, please.
  
  Thank you and best regards,
  Anand.

  >
  I created indexes for the less than 2500 separate keys, but we have 2 dimesions tables where there are great number of records (size 14 g and 10 g). Can I go ahead and create indexes of bitmap for 2 tables as well
  . . .
  Worried about creating index bitmap for large tables where they could affect the ETL process.
  >
  You put the cart before the horse!

  Don't create index unless you have a reason documented for them.

  Why did you choose the index bitmap for cardinality less than 2500? Perhaps based on a long-standing myth, but discredited on the cardinality?

  See also Richard Foote two articles where he explodes the myths about bitmap indexes and considerations of cardinality
  http://richardfoote.WordPress.com/2010/02/18/myth-bitmap-indexes-with-high-distinct-columns-blow-out/
  http://richardfoote.WordPress.com/2010/03/03/1196/

  Re your concern about the tables with the 'large' number of records and affecting ETL.

  You are right to be concerned about these issues, but you need to document your particular situation taking into account the architecture.

  The fact tables and dimension tables can have a large number of records. If using the bitmap index is indicated, then the most records are most effective, they will be.

  ETL is affected because the DML (INSERT, UPDATE, DELETE) operations on the tables with bitmap indexes can have serious performance because of the involved serialization issues. Updated single bitmap of a column value (e.g., am ' to 'F' gender) requires that the two index bitmap blocks must be blocked until the update is complete. An index of stored bitmap ranges ROWID (rowid min - max rowid) that can span many, many files. The "range" of ROWID is locked in order to change a value.

  To change: 'follow her' rowid beach so that a row is locked and ID should be removed from the range by turning off the bit. Change to the 'F', the rowid id range 'F' must be found, locked and the bit set that corresponds to this rowid. No another row with ROWID in the range cannot be changed, because it is a transaction in the series. If the range includes 1000 lines and they all need changed it takes 1000 series.

  For anything other that a very small number of documents the bitmap index would be deleted and rebuilt after the ETL operations. That is why the data warehouse designs try to minimize update and implement insertions and deletions using partitioning when possible; Adding a new day by adding a new partition.

  There is also a big difference between a bitmap index and a bitmap join index. The white paper you quoted does not really indicate what type are used or recommended.

  Learn more about the difference - see Using Bitmap indexes in data warehouses in the doc of Data Warehousing
  http://docs.Oracle.com/CD/B28359_01/server.111/b28313/indexes.htm

• DM 3.1 how to create a Bitmap Index?

  How to create a bitmap with SQL Developer Data Modeler 3.1 index? In the relational model, the properties of the General table allows to enumerate the indexes of a table and to clarify some of their attributes as such as columns and uniqueness. In addition, the properties of the plain index allows more options to set the properties of the index. Unfortunately, I'm unable to find the right place to specify that an index is an index of bitmap.
  
  However, maker of data tend to support bitmap indexes because the generated DDL statements for a table with bitmap indices, which was initially imported into the data dictionary, have correct index bitmap creation instructions. However, when I compare all B tree index with bitmap index in Data Modeler I can't find an option that specifies the index type as bitmap. So, I would be very happy if someone could tell me how to create bitmap with Data Modeler 3.1 indices.
  
  Best regards
  
  Miikka

  Hey Miikka,

  physical model is the place where you can define the specifications of database objects created in the relational model. So you open the physical model and you can find the node index under the node for the related table - use dialog for index set to the index of the bitmap image.

  Philippe

• The index of the bitmap on an already indexed attribute

  Hi all
  
  I am trying to create an index of vector on a (A1) attribute that is already a part of the non-unique clustered index. for example indexes (A1, A2, and A3) that is not unique.
  
  I get the below error:
  Error from line 14 in order:
  create index bitmap on acdelco_master (APPLICATION_NAME) idx_app_nm
  Error in the command line column: 14:49
  Error report:
  SQL error: ORA-01408: such list column already indexed
  01408 00000 - 'such list column already indexed.
  * Cause:
  * Action:
  
  When I look in the docs of Pracle on the bitmap index, I find the below
  
  Restrictions on the Bitmap index Bitmap indexes are subject to the following restrictions:
  
  •You cannot specify bitmap during the creation of a global partitioned index.
  
  •You cannot create an index secondary bitmap on a table held in index unless held in index table has a table mapping associated with it.
  
  •You cannot specify both UNIQUE and BITMAP.
  
  •You cannot specify a BITMAP for a domain index.
  (http://docs.oracle.com/cd/B19306_01/server.102/b14200/statements_5010.htm)
  
  No idea why I'm not able to create a bitmap index?

  See: http://asktom.oracle.com/pls/apex/f?p=100:11:0:P11_QUESTION_ID:42797723001361

• Cannot create a bitmap index

  Hello
  I want to create an index of bitmap on one of the columns in a table. I did request and it failed.

  SQL> CREATE BITMAP INDEX TRANS_N_BITMAPIDX_VEH_PLATFORM ON TRANSACTION_NEW(VEH_PLATFORM) LOCAL;
  
  Error starting at line 2 in command:
  CREATE BITMAP INDEX TRANS_N_BITMAPIDX_VEH_PLATFORM ON TRANSACTION_NEW(VEH_PLATFORM) LOCAL
  Error at Command Line:2 Column:70
  Error report:
  SQL Error: ORA-01408: such column list already indexed
  01408. 00000 -  "such column list already indexed"
  *Cause:    
  *Action:

  I found there is a NORMAL index combined with VEH_PLATFORM column called "IDX$ $_30AA00021. He followed columns
  
  • VEH_PLATFORM
  • VEH_MODEL
  • MODL_YR_NBR
  • VEH_MAKE
  • TXN_PROCS_DT
  
  But I was able to create bitmap index on columns VEH_MODEL, MODL_YR_NBR, and VEH_MAKE without any error.
  
  Why does error for the VEH_PLATFORM column?
  
  Kind regards
  Sam

  So the error message was true. You had already indexed this column

  INDEX_OWNER                    INDEX_NAME                     COLUMN_NAME                    COLUMN_POSITION
  ------------------------------ ------------------------------ ------------------------------ ---------------
  VISUAL                         TXN_INDX_PLATFORM1             VEH_PLATFORM                              1
  

  You cannot have two indexes exact same list of columns

  BTW, it's a whole lot of indexes on a table.

  Concerning
  Peter

• Local Bitmap Index confusion

  Hello
  I use Oracle 10.2.0.3.0 on Solaris 5.10.
  
  I have a range based to 60 partitions partition table. It is a fact table. I load the data for 60 days in this table. I created a partition for each day, and the partition key is the column date. I've created the table with the partition, but does not create the local bitmap index on the partition keys $vdate, because as far as I know oracle makes the local bitmap index unusable before insert you and then to rebuild it after the charge. Is this fair?
  
  So the best strategy is first load the data in the partition, and then create a local on this partition, is bitmap index - this exact?
  
  For example, in the future, some lines get inserted into an existing partition where the local bitmap index is present, then I should still once rebuild the index on that partition, as in the case of insertion Oracle would have it turned off?
  
  
  In this table, it has a vactivity column that is a foreign key to a dimension. Several queries use this column here where clause. I also want to create an index of bitmap on this column? On this not partitioned key column, the local bitmap index should be created. Is this fair?
  
  Please also suggest as which is faster, a local bitmap index rebuild after making it unusable, or the deletion and recreation it?
  
  Thank you and best regards

  If you insert only a few lines, you don't need to score the unusable bitmap index partition. The insert will not fail.

  However, if you perform a bulk insert several lines, it would be desirable mark it unusable and rebuild after insertion.

  You can certainly create an index on the column of the FK.

  Hemant K Collette

• Regarding the use of the Index

  Hello
  
  I have some doubts about the index:
  
  1. What is the difference between the 2 index usage scenarios below:
  / * + index (an index_name) parallel (a, 4) * /.
  / * + parallel_index(a,index_name,4) * /.
  
  Are the same two these?
  
  2. What is scan limited index complete and full scan index?
  
  3. I have a table in the database and there a few indexes on some columns. How can I check if the index is Bitmap or B-Tree?
  
  
  Thank you
  AB

  1. What is the difference between the 2 index usage scenarios below:
  / * + index (an index_name) parallel (a, 4) * /.
  / * + parallel_index(a,index_name,4) * /.
  Are the same two these?

  No,
  First of all the two boards, use the index and the other to indicate to the optimizer to use 4 simultaneous servers to a parallel operation are

  The second is just an indication. He tells the optimizer to use 4 concurrent servers on partitioned indexes.

  2. What is scan limited index complete and full scan index?

  The full index scan simple block reads.
  Full Fast scan do multi block reads.

  3. I have a table in the database and there a few indexes on some columns. How can I check if the index is Bitmap or B-Tree?

  In user_ | all_dba_indexes. Index_type will be BITMAP or NORMAL

  Concerning
  Peter

  PS: Speaking of tips. This favorite, can answer most of these questions, much better that I can:
  http://www.Oracle.com/pls/db112/homepage

  Published by: Peter on March 26, 2013 13:47

• Both indices should be bitmap when joining or not?

  I have a table with hundreds of K lines (should be in the millions within a few months, about 200 M in a few years) with a special column of smallint is a FK to a reference table. In the reference table, this is the PK and there are only about 500 values and it should pass very slowly, or not at all. The big table is responsible for all the days in a batch process, after which an update of statistics may be issued, if updates while the queries users is not a matter of concern.
  
  Am I right in assuming the ratio of 500 million + fact a candidate of good low cardinality for a bitmap index? The goal is equal between saving space and improving performance. Most of the queries join the reference because a very small subset (or a single) table of the possible values in the reference table is necessary, not all.
  
  If the index is intended to support the joining to the reference table, PK index on the table Ref should also be of type bitmap to make the most of the structure of the bitmap image?
  
  Thanks for any help!

  >
  I have a table with hundreds of K lines (should be in the millions within a few months, about 200 M in a few years) with a special column of smallint is a FK to a reference table. In the reference table, this is the PK and there are only about 500 values and it should pass very slowly, or not at all. The big table is responsible for all the days in a batch process, after which an update of statistics may be issued, if updates while the queries users is not a matter of concern.

  Am I right in assuming the ratio of 500 million + fact a candidate of good low cardinality for a bitmap index? The goal is equal between saving space and improving performance. Most of the queries join the reference because a very small subset (or a single) table of the possible values in the reference table is necessary, not all.

  If the index is intended to support the joining to the reference table, PK index on the table Ref should also be of type bitmap to make the most of the structure of the bitmap image?
  >
  Your use case would not be appropriate for a bitmap index.

  Bitmap indexes provide benefits when used in combination with other clues bitmap on the same table. These fine Oraclel can manipulate the index bitmap against the other two ((A AND B) OR C AND D) very effective to identify lines of interest.

  You shall not create either join as a bitmap index index.

  See the Guide to data warehousing for more information on bitmap index and how and when to use
  http://docs.Oracle.com/CD/B28359_01/server.111/b28313/indexes.htm
  >
  Bitmap indexes are most effective for queries that contain multiple conditions in the WHERE clause. The lines that meet some, but not all, conditions are filtered before the table itself is accessible. This improves response time, often in spectacular fashion. If you are not sure of the index to create, SQL Access Advisor can generate recommendations on what to create. As bitmaps bitmap indexes can be combined quickly, it is usually best to use column indexes unique bitmap.

• Remote index not used with INSERT in the local table on dblink

  Hi all
  
  I don't know if anyone has come across this problem before, but for some reason any the remote index remains unused ONLY* in the insertion on the local database operation. Let me explain this pseudo-device code
  
  insert into LOCAL_TABLE
  Select / * + index_combine (alias_remote_tab IDX_LOG_DATE) * /.
  trunc (log_datetime),
  Count (*)
  of REMOTE_TABLE@DBLINK alias_remote_tab
  When trunc (log_datetime) = trunc(sysdate-1)
  Trunc Group (log_datetime);
  
  where:
  REMOTE_TABLE is a table partitioned on log_datetime (monthly)
  IDX_LOG_DATE is an index of bitmap of based on a valid function on log_datetime created in the trunc (log_datetime)
  local database: 10 gr 2
  remote database: 11 GR 1 material
  OS: windows (both)
  
  More funny thing is when I just run the select query independently on the only both local and remote, the index is used. I checked by printing the command explain for the select query plan. But when I prefix the query with the insert lose all hell breaks and local database plays the ignorance about the index. The command for the insert query explain plan has no mention of the index even when I explicitly place the index indicator in the select part of the query.
  
  If this should not be simple enough for ORACLE? Am I missing something here?

  Jonathan describes the details and the reasons for the behavior you see in following blog post http://jonathanlewis.wordpress.com/2008/12/05/distributed-dml/
  Your SELECTION is performed remotely (filtering and grouping) and sends only the (relatively) small results via dblink local database while the in an INSERTION, filtering only occurs at the remote and data site (relatively) important are sent via dblink to the local database, the consolidation takes place.
  You can give a try to the approach proposed by michaels2. If the approach from the view result grouping and filtering which will take place in the remote database, you will see improved performance.

  PS BTW, if the sql code that I suggested to check the plane, in my previous post using an index, then the cause of your performance issue is certainly not due to the index not used and is due to the amount of data transferred to dblink.

• Rebuild partition/subpartition in parallel

  Hello

  I'm on 11 GR 2.

  I have a composite partitioned table.

  I have the index local bitmap created with the parallel clause. no degree specified and left to "DEFAULT".

  I made the unusable index for some of the subparts.

  Now, I want to rebuild the local indexes on the server.

  alter index < index_name > < partition name > rebuild subpartition;

  Given that these indices were initially created with parallel clause, do I need to explicitly specify the parallel clause for them to be rebuilt at the same time?

  EDIT:

  I've tested this and it seems that I have to specify the parallel clause explicitly for the index to rebuild at the same time. Without the parallel clause, the index used only a thread to do the work.

  Mark as answer and closed.

  Responded. We need to explicitly specify

• Calculation of the cardinality.

  Hello

  Selectivity is the fraction of rows in the rowset that meets the requirement of predicate.
  It can be calculated as the inverse of the number of separate in the column lines, if the distinct values in the column are distributed evenly.
  If the distinct values in the column are not distributed evenly then optimizer search histogram for selectivity.

  
  Cardinality refers to the number of rows in the rowset.
  Can it be calculated as selectivity * num_rows in the table/column?

  
  In the Bitmap Index.
  We used to create indexes of bitmap on a column, whose cardinality is low.
  Here the cardinality can be calculated by:-num_distinct_rows/total_num_rows

  
  My question is, what is the difference between the cardinality of the optimizer and the cardinality based on which the Bitmap index is created?

  Thank you

  The total number of lines is not a parameter

  That's a setting BOTH the 'hand' two parameters to determine the selectivity and the determination of costs that will determine if an index can be used or not.

  1 - total number of lines to select

  2. total number of lines to select the

  Oracle decide NOT to use an index just because the result may contain 1 million rows. But if the table has only 1 million lines then it can get these lines by using a full table rather than an index scan.

  Or if the table contains rows 1 billion so the index will be suddenly much more attractive.

  As part of a 1 million line table the term 'little' may not apply if you're talking about 1 million rows. But 1 million lines is indeed "little" in the context of this 1 billion row table.

  That's why I said the word 'little' has little or no sense. There must be a meaningful 'context'

  And when the glossary speak of a threshold of 1% in the "degree of cardinality", in my humble OPINION both the term and the definition is wrong.

  Sure - this 1% threshold ' part is bad, but it is related to the bitmap index and has NOTHING to do with the definition of the degree of cardinality provided.

  Not to argue with the basic premise - just try to clarify things a little.

• Photoshop CC 2015 on Surface pro 3 will not draw on the new layers

  Photoshop CC 2015. It works fine on my PC, but on my Surface 3 pro it only allow me to draw on the background layer and nothing else. Help, please!

  What happens when you try to create a new layer, or if you can, change another layer? You can post a screenshot? Looks like your document's index or bitmap color mode.