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:
“So long as the source of our identity is external—vested in how others judge our performance at work, or how others judge our children’s performance, or how much money we make—we will find ourselves hopelessly flawed, forever short of the ideal.”
—Melinda M. Marshall (20th century)
“Unless, governor, teacher inspector, visitor,
This map becomes their window and these windows
That open on their lives like crouching tombs
Break, O break open,”
—Stephen Spender (1909–1995)
“Art is the imposing of a pattern on experience, and our aesthetic enjoyment is recognition of the pattern.”
—Alfred North Whitehead (1861–1947)