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Posted to derby-dev@db.apache.org by "Knut Anders Hatlen (JIRA)" <ji...@apache.org> on 2007/07/19 09:20:04 UTC
[jira] Resolved: (DERBY-2878) Scan protection handle could be
cached in BasePage
[ https://issues.apache.org/jira/browse/DERBY-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Knut Anders Hatlen resolved DERBY-2878.
---------------------------------------
Resolution: Fixed
Fix Version/s: 10.4.0.0
Committed 3a with revision 557507.
> Scan protection handle could be cached in BasePage
> --------------------------------------------------
>
> Key: DERBY-2878
> URL: https://issues.apache.org/jira/browse/DERBY-2878
> Project: Derby
> Issue Type: Improvement
> Components: Performance, Store
> Affects Versions: 10.4.0.0
> Reporter: Knut Anders Hatlen
> Assignee: Knut Anders Hatlen
> Priority: Minor
> Fix For: 10.4.0.0
>
> Attachments: derby-2878-1.diff, derby-2878-1.stat, derby-2878-1b.diff, derby-2878-2.diff, derby-2878-3.diff, derby-2878-3.stat, derby-2878-3a.diff
>
>
> Each time a leaf node in a B-tree is visited in an index scan, a scan protection row is locked and unlocked. Both the lock operation and the unlock operation will allocate a new RecordId object representing the scan protection row (the unlock operation additionally allocates a PageKey object for the RecordId). Since the scan protection handle created will be identical (seen from equals()) each time it is created for a page, it would make sense to cache it in BasePage. Then we only need to allocate the protection handle for a page once for as long as it stays in the page cache. This would save three object allocations per single-record lookup via index.
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