Dirty read
A dirty read is a concurrency anomaly in which a transaction reads data written by another transaction before that transaction commits.
Java Persistence with Spring Data and Hibernate epub
A dirty read is a concurrency anomaly in which a transaction reads changes made by another transaction before those changes are committed.
- How it is used
- Explains a transaction anomaly that motivates selecting an appropriate isolation level.
- How deep it goes
- Defines the transaction sequence and rollback danger, then places the anomaly within isolation-level comparisons.
- Examples
- Uses a two-transaction timeline in which Transaction 2 reads Transaction 1's uncommitted change.
- What you can do after
- Evaluate transaction isolation choices by recognizing when reads can observe data that may later roll back.
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100 SQL Server Mistakes and How to Avoid Them
A dirty read is the retrieval of data changed by another transaction before that change has been committed.
- How it is used
- Warns against using Read Uncommitted to reduce lock contention when reporting reads can encounter uncommitted updates.
- How deep it goes
- Demonstrates the update, reporting query, and rollback sequence, while stopping short of database-engine internals.
- Examples
- Uses a MarketingArchive BidPrice update, a campaign SUM report, and a rollback across two query windows.
- What you can do after
- Diagnose dirty reads with paired T-SQL transactions and choose Read Committed instead of unsafe performance shortcuts.
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Related concepts
- read committed isolation leveladdressed by · A database transaction isolation level that prevents reads of uncommitted changes while allowing later reads in a transaction to observe newer committed data.
- read uncommittedproduced by · Read uncommitted is a transaction isolation level that allows a transaction to read data written by other transactions before those changes are committed.
- snapshot isolationaddressed by · Snapshot isolation is a transaction-isolation method in which each transaction reads a consistent versioned snapshot of committed data while concurrent writes are isolated from that view.
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