In the design of
DBMS
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases s ...
, the identity map pattern is a database access
design pattern
A design pattern is the re-usable form of a solution to a design problem. The idea was introduced by the architect Christopher Alexander and has been adapted for various other disciplines, particularly software engineering. The "Gang of Four" boo ...
used to improve performance by providing a context-specific, in-memory
cache
Cache, caching, or caché may refer to:
Places United States
* Cache, Idaho, an unincorporated community
* Cache, Illinois, an unincorporated community
* Cache, Oklahoma, a city in Comanche County
* Cache, Utah, Cache County, Utah
* Cache County ...
to prevent duplicate retrieval of the same object data from the database.
If the requested data has already been loaded from the database, the identity map returns the same instance of the already instantiated object, but if it has not been loaded yet, it loads it and stores the new object in the map. In this way, it follows a similar principle to
lazy loading
Lazy loading (also known as asynchronous loading) is a design pattern commonly used in computer programming and mostly in web design and development to defer initialization of an object until the point at which it is needed. It can contribute to ef ...
.
There are 4 types of identity maps
#Explicit
#Generic
#Session
#Class
See also
*
Active record In software engineering, the active record pattern is an architectural pattern. It is found in software that stores in-memory object data in relational databases. It was named by Martin Fowler in his 2003 book ''Patterns of Enterprise Application ...
*
Identity function
Graph of the identity function on the real numbers
In mathematics, an identity function, also called an identity relation, identity map or identity transformation, is a function that always returns the value that was used as its argument, un ...
*
Map (mathematics)
In mathematics, a map or mapping is a function in its general sense. These terms may have originated as from the process of making a geographical map: ''mapping'' the Earth surface to a sheet of paper.
The term ''map'' may be used to distingu ...
*
Lazy loading
Lazy loading (also known as asynchronous loading) is a design pattern commonly used in computer programming and mostly in web design and development to defer initialization of an object until the point at which it is needed. It can contribute to ef ...
References
Architectural pattern (computer science)
Articles with example C Sharp code
Software design patterns
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