Introduction to Bitmap Indexes

Introduction to Bitmap Indexes

To alleviate confusion, I will refer to bit-indexing and bit mapped indexing as a bitmap index.  Through my research I have seen these terms used interchangeably to define the same concept – bitmap indexes.

What is a bitmap index and how do they work?

Bitmap indexes are a mechanism, largely employed by Oracle databases, to increase search performance on large data sets.  Bitmap indexes are most effective when applied to columns that exhibit low cardinality.  In this case, cardinality represents the amount of unique values that a column may contain.  For example, a column called “Active” on a user account table would likely only contain two values: true or false (or active and disabled).  Regardless of the total number of tuples,  the values contained in this column is only two possible values.  This column exhibits low cardinality.  A column that exhibits high cardinality benefit less from creating an index on them and become candidates for a primary key – that is if each tuple contains a unique value. Continue reading

Drupal SQL Injection Vulnerability

Drupal SQL Injection – SA-CORE-2014-005

This posting discusses the Drupal SQL Injection vulnerability from https://www.drupal.org/SA-CORE-2014-005, which affected Drupal versions 7.0 – 7.31.  This security announcement was released on October 15, 2014 and was marked as Highly Critical.  By October 29th, the Drupal Security Team posted a follow-on Public Service Announcement (PSA), https://www.drupal.org/PSA-2014-003, which warned that all Drupal sites should be considered compromised if not patched by Oct 15th, 11pm UTC – only seven hours after the initial security release! Continue reading