In the design of database management systems, the identity map pattern is a database access design pattern used to improve performance by providing a context-specific, in-memory cache 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.
There are four types of Identity Map
- Explicit
- Generic
- Session
- Class
Famous quotes containing the words identity, map and/or pattern:
“Motion or change, and identity or rest, are the first and second secrets of nature: Motion and Rest. The whole code of her laws may be written on the thumbnail, or the signet of a ring.”
—Ralph Waldo Emerson (1803–1882)
“In thy face I see
The map of honor, truth, and loyalty.”
—William Shakespeare (1564–1616)
“It was her stern necessity: all things
Are of one pattern made; bird, beast, and flower,
Deceive us, seeming to be many things,
And are but one. Beheld far off, they differ
As God and devil; bring them to the mind,
They dull its edge with their monotony.”
—Ralph Waldo Emerson (1803–1882)