Skip to main content

Oracle 12C 'Bitmap Index' benefits over B-tree Index

Oracle 12C 'Bitmap Index' benefits over B-tree Index
#Oracle 12C 'Bitmap Index' benefits over B-tree Index:
A bitmap index has a significantly different structure from a B-tree index in the leaf node of the index. It stores one string of bits for each possible value (the cardinality) of the column being indexed.

Note: One string of BITs means -Each tupple of possible value it assigns '1' bit in a string.So, all the BITs become a string ( This is an example, on which column you created BIT map index)

The length of the string of bits is the same as the number of rows in the table being indexed.

In addition to saving a tremendous amount of space compared to traditional indexes, a bitmap index can provide dramatic improvements in response time because Oracle can quickly remove potential rows from a query containing multiple WHERE clauses long before the table itself needs to be accessed.

Multiple bitmaps can use logical AND and OR operations to determine which rows to access from the table.

Although you can use a bitmap index on any column in a table, it is most efficient when the column being indexed has a low cardinality, or number of distinct values.

For example, the GENDER column in the PERS table will be either NULL, M, or F. The bitmap index on the GENDER column will have only three bitmaps stored in the index. On the other hand, a bitmap index on the LAST_NAME column will have close to the same number of bitmap strings as rows in the table itself. The queries looking for a particular last name will most likely take less time if a full table scan is performed instead of using an index. In this case, a traditional B-tree non-unique index makes more sense.

A variation of bitmap indexes called bitmap join indexes creates a bitmap index on a table column that is frequently joined with one or more other tables on the same column. This provides tremendous benefits in a data warehouse environment where a bitmap join index is created on a fact table and one or more dimension tables, essentially pre-joining those tables and saving CPU and I/O resources when an actual join is performed.


Popular posts from this blog

Four Tableau products a quick review and explanation

I want to share you what are the Products most popular.

Total four products. Read the details below.

Tableau desktop-(Business analytics anyone can use) - Tableau  Desktop  is  based  on  breakthrough technology  from  Stanford  University  that  lets  you drag & drop to analyze data. You can connect to  data in a few clicks, then visualize and create interactive dashboards with a few more.

We’ve done years of research to build a system that supports people’s natural  ability  to  think visually. Shift fluidly between views, following your natural train of thought. You’re not stuck in wizards or bogged down writing scripts. You just create beautiful, rich data visualizations.  It's so easy to use that any Excel user can learn it. Get more results for less effort. And it’s 10 –100x faster than existing solutions.

Tableau server
Tableau  Server  is  a  business  intelligence  application  that  provides  browser-based  analytics anyone can use. It’s a rapid-fire alternative to th…

The Sqoop in Hadoop story to process structural data

Why Sqoop you need while working on Hadoop-The Sqoop and its primary reason is to import data from structural data sources such as Oracle/DB2 into HDFS(also called Hadoop file system).
To our readers, I have collected a good video from Edureka which helps you to understand the functionality of Sqoop.

The comparison between Sqoop and Flume

The Sqoop the word came from SQL+Hadoop Sqoop word came from SQL+HADOOP=SQOOP. And Sqoop is a data transfer tool. The main use of Sqoop is to import and export the large amount of data from RDBMS to HDFS and vice versa. List of basic Sqoop commands Codegen- It helps to generate code to interact with database records.Create-hive-table- It helps to Import a table definition into a hiveEval- It helps to evaluateSQL statement and display the resultsExport-It helps to export an HDFS directory into a database tableHelp- It helps to list the available commandsImport- It helps to import a table from a database to HDFSImport-all-tables- It helps to import tables …

Different Types Of Payment Cards

The Credit Card (Shopping): The purpose o this card is to buy any item withing the limit prescribed by banks to cardholder. These cards can have both Magnetic stripe and Chip cards. 
Now a days all banks are issuing credit cards with CHIP and PIN. After entering the PIN by cardholder, then transaction starts for further processing.

The debit (ATM, Cash) card is a relatively new method of payment. It is different from a credit card because the debit cardholder pays with the money available in their bank account, which is debited immediately in real time. A debit card seems to be more dangerous compared to a credit card because the debit card is directly linked to the bank checking account and usually allows ATM cash withdrawals.

On the other hand, it is more protected by the required two-factor authentication (PIN number plus card itself). The real dangerous element of many branded debit cards is that they can be processed as credit cards, without entering the PIN.

The Gift card
is simila…