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cached lock_sys hash value in block descriptor
Posted by: Chen Fu
Date: October 13, 2019 11:05AM

It seems to me that the field lock_hash_val in the buffer pool block descriptor is for caching the lock_sys hash value.

Am I understanding it right? if so, why? computing it seems only involve 8 simple ALU operations? the difference between loading it from lock_hash_val vs computing it on the fly seems to be only several cycles. Did I miss something important?

This lock_hash_val field needs to be maintained in multiple places. for example, during lock_sys resize, buffer pools must be locked and each non-empty page must be updated.

is there consideration to remove this field?

Thanks!

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cached lock_sys hash value in block descriptor
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October 13, 2019 11:05AM


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