Indexes

• Data structure used to speed access to tuples of a relation, given one or more attributes
• CREATE INDEX <name> ON <table>(<attrs>)
• Using
  • Given a value v, the index takes us to only those tuples that have v in the attributes of the index
• For multi-value indexes, the values are concatenated in order
  • That means it considers the first attribute first
• Implemented using a B Tree or a Hash Table

Database Tuning

• Which indexes and views to create
• Can either be manual or automatic
  • Tuning advisors is a major area of research
• Index Impact
  • Pro: An index speeds up queries that use it
  • Con: An index slows down all modification because the index must be modified too