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Date: Sun, 18 Mar 2007 06:50:10 -0700 (PDT)
From: "Knut Anders Hatlen (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-2114) Let Clock embed a HashMap rather
 than inherit from Hashtable
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    [ https://issues.apache.org/jira/browse/DERBY-2114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12481937 ] 

Knut Anders Hatlen commented on DERBY-2114:
-------------------------------------------

Thank you for addressing my comments! There is one thing I missed in the previous review:

+	public boolean containsKey(Object k) {
+		synchronized(cache_) {

+	public Collection values() {
+		synchronized (cache_) {

I believe these two methods should have been synchronized on this, not on cache_. I have made that change to the patch and started the regression tests. Will commit if the tests don't fail.

> Let Clock embed a HashMap rather than inherit from Hashtable
> ------------------------------------------------------------
>
>                 Key: DERBY-2114
>                 URL: https://issues.apache.org/jira/browse/DERBY-2114
>             Project: Derby
>          Issue Type: Improvement
>          Components: Performance
>    Affects Versions: 10.2.1.6
>            Reporter: Dyre Tjeldvoll
>         Assigned To: Dyre Tjeldvoll
>            Priority: Trivial
>             Fix For: 10.3.0.0
>
>         Attachments: derby-2114.v1.diff, derby-2114.v1.stat, derby-2114.v2.diff, derby-2114.v2.stat
>
>
> Clock currently inherits from Hashtable, but the use of Hashtable is really an implementation detail that would benefit from being hidden as private member. All access to the hashtable happens inside sychronized blocks so it is safe to substitute a HashMap. This change appears to trigger a small increase in throughput, as measured by the average TPS number obtained by running the select client from DERBY-1961 repeatedly.

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