Slideshow:
Index type 1: ordered index
Index type 2: hash index
Effect of an index
It will help limit the search space
- There are 2 basic kinds
of indexes:
-
Ordered indexes
- The search keys are
stored in
sorted order
inside the
index file
Schematically:
We can find a search key in the index file quickly using binary search !!!
- The search keys are
stored in
sorted order
inside the
index file
-
Hash indexes
- The search keys are
stored in
hash buckets.
- Each hash bucket is stored as a 1 or more blocks in the index file
Schematically:
We can find the disk blocks containing the search key quickly by using the hash function
- The search keys are
stored in
hash buckets.
-
Ordered indexes
- An index will
achieve this
effect:
In other words:
- An index performs the
following mapping:
Search key value ======> List of blocks that contains the search key value
- An index performs the
following mapping: