statedb: Fix read-after-write bug #31164
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The optimization to reuse the last used "indexReadTxn" was broken when a WriteTxn was first used for a read and then for a write followed by a read (the last read re-used an old transaction). Add test to observe this bug. Signed-off-by: Jussi Maki <jussi@isovalent.com>
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The optimization in *txn to hold the last used index read transaction to avoid a hash map lookup was broken as the write txn used for reading was cloned, leading to not being able to read any of the future writes in the same transaction. Benchmark show that this optimization does not actually help, so solve the problem by removing the optimization. Before: BenchmarkDB_RandomLookup-8 1000000 1471 ns/op After: BenchmarkDB_RandomLookup-8 1000000 1485 ns/op Fixes: d0d4d46 ("statedb: Store index unique info in the index tree entry") Signed-off-by: Jussi Maki <jussi@isovalent.com>
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bimmlerd
approved these changes
Mar 6, 2024
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statedb: Fix read-after-write bug
The optimization in *txn to hold the last used index read transaction
to avoid a hash map lookup was broken as the write txn used for reading
was cloned, leading to not being able to read any of the future writes
in the same transaction.
Benchmark show that this optimization does not actually help, so solve
the problem by removing the optimization.
Before:
BenchmarkDB_RandomLookup-8 1000000 1471 ns/op
After:
BenchmarkDB_RandomLookup-8 1000000 1485 ns/op
Fixes: d0d4d46 ("statedb: Store index unique info in the index tree entry")
Note that v1.14 does not have the "StateDB v2.0", so it is not affected by this.