Phantom Read
A transaction anomaly in which repeating a predicate query returns a different set of rows because another transaction inserted or removed matching rows.
Database Context
A phantom read occurs when repeating a predicate query yields a different set of matching rows because another transaction inserted or removed rows in the range. Serializable validation, predicate or range locking, and some MVCC isolation mechanisms are used to prevent the anomaly.
Isolation Boundary
A changed value in an already-read row is a non-repeatable read. A phantom concerns the membership of the result set itself.
Related Database Concepts
- Serializability
- Predicate Lock
- Non-Repeatable Read
- MVCC