Entry

what is indexing and hashing?

May 13th, 2008 20:58
dman, i can do it, Praveen sehrawat, kenneth clement, http://sturly.com

Indexing is defined as auxiliary data  structure to speed up 
operations. Index works with the principle of search key and index 
file. Indexing is used to speed up operations which are not supported 
by the basic organization of records in the file. Search key is 
defined as attributes or set of attributes used to look up records 
whereas an index file is an collection of data entries supporting the 
efficient retrieval of all data records with a given key value.  
Hashing is a part of indexing which is termed as unordered indices or 
hash based indicies, There are two types of hashing static hashing and 
dynamic hashing. Dynamic hashing is further divided into extensible 
and linear hashing. 
Hash based indices are divided into two categories 
1.	Hashing for disk files which is also called as external 
hashing :-  This is the type of hashing which is done in memory within 
program. It takes into account that the records are stored in block 
pages. 
2.	Basic or static hashing :-  It is the type of hashing which 
allocates a fixed number of buckets and it keep a check for the 
overflow blocks in a bucket which are chained together.