[DERBY-4512] Avoid unnecessary lookup in transaction table when adding transaction

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 10.6.1.0
• Fix Version/s: 10.6.1.0
• Component/s: Store
• Bug behavior facts: Performance
• Assignee: Knut Anders Hatlen
• Reporter: Knut Anders Hatlen
• Created: 12/Jan/10 14:09
• Updated: 19/Jan/10 10:37
• Resolved: 19/Jan/10 09:58

Description

TransactionTable.add() first checks if the Hashtable trans contains a transaction with the same id as the one being added. If it does, add() does nothing. If there is no such transaction, a new TransactionTableEntry is created and put into the Hashtable.

I believe that TransactionTable.add() is never called on a transaction that has already been added to the table. If this is the case, there's no point in checking the Hashtable first. Instead, we could just create a new TransactionTableEntry and add it unconditionally. This would reduce the number of (synchronized) Hashtable calls and could improve the performance in scenarios like the one described in DERBY-3092.

Issue Links

• is related to: DERBY-4517 Unnecessary synchronization in TransactionTable.add()
• relates to: DERBY-3092 Use java.util.concurrent in TransactionTable to improve scalability