Unnecessary synchronization in TransactionTable.add()
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Key: DERBY-4517
URL: https://issues.apache.org/jira/browse/DERBY-4517
Project: Derby
Issue Type: Improvement
Components: Store
Affects Versions: 10.6.0.0
Reporter: Knut Anders Hatlen
Priority: Minor
impl.store.raw.xact.TransactionTable.add() has a synchronized block around the
code that adds a transaction to the transaction table. It synchronizes on
"this".
My understanding of the synchronization in the TransactionTable class is that
synchronization on "this" is only used to give a consistent view of the set of
update transactions. It is typically used to guard state transitions for
transactions from read to update, removal of update transactions from the
table, and writing the update transactions to the log during checkpointing.
No transition to/from update happens in this synchronized block (the entry
that's added is initialized with the update flag cleared), so I believe that
the synchronization could be removed. The code will still be implicitly
synchronized on the Hashtable so that it should be safe to access it from
multiple threads.
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