thetumbled commented on PR #18390:
URL: https://github.com/apache/pulsar/pull/18390#issuecomment-1308100085
> But I'm still not sure about the following logic
>
> ```java
> // First try optimistic locking
> long storedKey1 = table[bucket];
> long storedKey2 = table[bucket + 1];
> long storedValue1 = table[bucket + 2];
> long storedValue2 = table[bucket + 3];
>
> if (!acquiredLock && validate(stamp)) {
> // The values we have read are consistent
> if (key1 == storedKey1 && key2 == storedKey2) {
> return new LongPair(storedValue1,
storedValue2);
> ```
>
> Even if storedKey1 and storeKey2 matched the expected keys, are
storedValue1 and storedValue2 guaranteed to be exactly the associated values?
This PR covered the case that table is shrinking, which makes the index
invalid. However, could it happen that when retrieving `table[bucket + 2]` and
`table[bucket + 3]`, these values have been modified? @lhotari @lordcheng10
@thetumbled
if `table[bucket + 2]` and `table[bucket + 3]` is modified, there must be
one thread having acquired write lock, which result into that `validate(stamp)`
return false and fallback to pessimistic read.
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