Understanding Concurrency
Here's a concise explanation of the Concurrency concepts of Dirty Reads, Non-Repeatable Reads, Phantom Reads, and Write-Write Conflicts in tabular format for clear understanding:
| Description |
| Dirty Reads | Occurs when a transaction reads data that has been written by another transaction that is not yet committed. This can lead to issues if the other transaction is rolled back, as the read data might never have been committed. |
| Non-Repeatable Reads | Happens when a transaction reads the same row twice and finds different data each time, because another transaction has modified or committed changes to that row after the first read. |
| Phantom Reads | Arises when a transaction re-executes a query for a range of rows and discovers rows that weren't there previously due to another committed transaction. This can occur when new rows are added (or existing ones are deleted) that meet the query criteria. |
| Write-Write Conflict | Occurs when two transactions attempt to update the same row at nearly the same time. The last transaction to commit will overwrite changes made by the first, potentially leading to lost updates if not properly managed.
|
These concepts are fundamental to understanding transaction isolation levels and their implications on database operations, particularly regarding data consistency and integrity in concurrent transaction environments.
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