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Date: Thu, 28 Jun 2007 08:50:25 -0700 (PDT)
From: "Knut Anders Hatlen (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-2878) Scan protection handle could be cached
 in BasePage
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     [ https://issues.apache.org/jira/browse/DERBY-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Knut Anders Hatlen updated DERBY-2878:
--------------------------------------

    Attachment: derby-2878-1.stat
                derby-2878-1.diff

Attached is the first step towards eliminating the allocation of protection handles. It adds a method to Page/BasePage called getProtectionRecordHandle(). This method creates a new record handle if it hasn't been called before and returns a cached value otherwise. B2IRowLocking3.lockScan() and lockScanForReclaimSpace() have been modified to use the new method.

unlockScan() still allocates a protection handle since it cannot access the page object, but it should be fairly easy to make it reuse the handle too.

suites.All and derbyall passed.

> 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
>         Attachments: derby-2878-1.diff, derby-2878-1.stat
>
>
> 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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