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Type:
Improvement
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Resolution: Fixed
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: Transactions
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Storage Engines
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2
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2024-08-06 - Withholding Tax
Since a very old commit we've had this code in the __wt_txn_id_alloc function:
id = __wt_atomic_addv64(&txn_global->current, 1) - 1;
The comment above the code reads:
so we want post-increment semantics. Our atomic add primitive does pre-increment, so adjust the result here.
It seems like at the time the fetch_add primitive did not exist in WiredTiger. Which means we can simplify this line of code to:
id = __wt_atomic_fetch_addv64(&txn_global->current, 1);
This will return the value pre-increment, and be the correct way of doing what the code aims to atomically.
Scope:
- Replace both occurrences with fetch_add.
- Run stress testing on the change.