[jira] Closed: (DERBY-4512) Avoid unnecessary lookup in transaction table when adding transaction

["Knut Anders Hatlen (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-4512?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Knut Anders Hatlen closed DERBY-4512.
-------------------------------------

          Resolution: Fixed
       Fix Version/s: 10.6.0.0
    Issue & fix info:   (was: [Patch Available])

Committed revision 900714.

> Avoid unnecessary lookup in transaction table when adding transaction
> ---------------------------------------------------------------------
>
>                 Key: DERBY-4512
>                 URL: https://issues.apache.org/jira/browse/DERBY-4512
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store
>    Affects Versions: 10.6.0.0
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
>             Fix For: 10.6.0.0
>
>         Attachments: assert.diff, txtab-noblanks.diff, txtab.diff
>
>
> 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.

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